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<title>Life Lexicon (P)</title>
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<center><A HREF="lex.htm">Introduction</A> | <A HREF="lex_bib.htm">Bibliography</A></center></center>
<hr>
<center>
<b>
<A HREF="lex_1.htm">1-9</A> |
<A HREF="lex_a.htm">A</A> |
<A HREF="lex_b.htm">B</A> |
<A HREF="lex_c.htm">C</A> |
<A HREF="lex_d.htm">D</A> |
<A HREF="lex_e.htm">E</A> |
<A HREF="lex_f.htm">F</A> |
<A HREF="lex_g.htm">G</A> |
<A HREF="lex_h.htm">H</A> |
<A HREF="lex_i.htm">I</A> |
<A HREF="lex_j.htm">J</A> |
<A HREF="lex_k.htm">K</A> |
<A HREF="lex_l.htm">L</A> |
<A HREF="lex_m.htm">M</A> |
<A HREF="lex_n.htm">N</A> |
<A HREF="lex_o.htm">O</A> |
<A HREF="lex_p.htm">P</A> |
<A HREF="lex_q.htm">Q</A> |
<A HREF="lex_r.htm">R</A> |
<A HREF="lex_s.htm">S</A> |
<A HREF="lex_t.htm">T</A> |
<A HREF="lex_u.htm">U</A> |
<A HREF="lex_v.htm">V</A> |
<A HREF="lex_w.htm">W</A> |
<A HREF="lex_x.htm">X</A> |
<A HREF="lex_y.htm">Y</A> |
<A href="lex_z.htm">Z</A></b>

</center>
<hr>
<p><a name=p>:</a><b>p</b> = <a href="#period">period</a>
<p><a name=p1>:</a><b>p1</b> Period 1, i.e., <a href="lex_s.htm#stable">stable</a>. In the context of logic <a href="lex_c.htm#circuit">circuitry</a>,
this tends to mean that a mechanism is constructed from
<a href="lex_h.htm#herschelconduit">Herschel conduits</a> that contain only <a href="lex_s.htm#stilllife">still lifes</a> as <a href="lex_c.htm#catalyst">catalysts</a>.
In the context of <a href="lex_s.htm#slowgliderconstruction">slow glider construction</a>, a P1 <a href="lex_s.htm#slowsalvo">slow salvo</a> is
one in which there are no constraints on the <a href="#parity">parity</a> of gliders in
the salvo, because the <a href="lex_i.htm#intermediatetarget">intermediate targets</a> are all stable
constellations. (The usual alternative is a "P2 slow salvo", where
the relative timing between adjacent gliders can be increased
arbitrarily, but only by multiples of two ticks.)
<p><a name=p104gun>:</a><b>p104 gun</b> A <a href="lex_g.htm#glidergun">glider gun</a> with period 104, found by Noam Elkies on 21
March 1996. It is based on an <a href="lex_r.htm#rpentomino">R-pentomino</a> <a href="lex_s.htm#shuttle">shuttle</a> reaction.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OO........OO..........................$.OO.........O.......O..................$.OO.........O.OO...O.O............OO...$.O...........O......O.............OOO..$O.O......OO......O................OO.O.$O.OO.....OO....O....................O.O$................O..................O..O$....................................OO.$.OO....................................$.OO....................................$...............OO......................$................OO..................OO.$................O...................OO.$.OO......OOO........................OO.$O..O.......O........................O..$O.O.........................OO.....O.O.$.O.OO.......................OO.....O.OO$..OOO.............O....................$...OO............O.O...................$..................O.................OO.$....................................OO.$"
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....................................OO.
</a></pre></td></tr></table></center>
<p><a name=p11bumper>:</a><b>p11 bumper</b> (p11) A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a>
with a minimum <a href="lex_r.htm#repeattime">repeat time</a> of 44 ticks. Unlike the p5 through p8
cases where Noam Elkies' <a href="lex_d.htm#domino">domino</a>-spark based reflectors are
available, no small period-22 <a href="lex_c.htm#colourchanging">colour-changing</a> reflector is known.
A <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a> reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>.
This changes the timing of the output glider, which can be useful for
rephasing periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:............................O..$............................O.O$............................OO.$...............................$...............................$...............................$...............................$...............................$...............................$...............................$...............................$.................O.............$.................O.O...........$.................OO............$...............................$.........OO....OO..............$.........OO...O..O.............$...OO....OO....O.O.............$....O.....OO....O..............$..O.....O.OO...................$..OO..OOO...........OO.........$.....O....O.O.......O..........$..OOO.OO.OO.OOO......OOO.......$.O....O....O...O.......O.......$O.O.O...OO.O..O................$O.O......O.O.O.................$.O..OOOOO..OO..................$..OO....O.O....................$....OOOO..O....................$..OO......OO...................$..O..O.........................$....OO.........................$"
>............................O..
............................O.O
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..OO..OOO...........OO.........
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.O....O....O...O.......O.......
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.O..OOOOO..OO..................
..OO....O.O....................
....OOOO..O....................
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....OO.........................
</a></pre></td></tr></table></center>
<p>In practice this reflector is not useful with input streams below
period 121, because lower-period bumpers can be used to reflect all
smaller multiples of 11 for which the bumper reaction can be made to
work.
<p><a name=p130shuttle>:</a><b>p130 shuttle</b> A <a href="lex_s.htm#shuttle">shuttle</a> found in March 2004 by David Eppstein, which
originally needed several period 5 oscillators for support. David
Bell found a reaction between two of the shuttles to produce a p130
glider gun. On 18 November 2017 Tanner Jacobi found that the
<a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#sidesnagger">sidesnagger</a> can be used to support the shuttle instead,
and this is shown here.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....OO................................OO.....$.....OO................................OO.....$..............................................$..............................................$.........................O....................$OO....OO..................O...........OO....OO$OO...O..O................OO..........O..O...OO$.....O.O...........OOOOOOO............O.O.....$......O...........OOO..O...............O......$..................O..OO.O.....................$...O..................O.O.................O...$..O.O...............OO.OO................O.O..$..OO................OOOO..................OO..$..............................................$..OO................OOOO..................OO..$..O.O...............OO.OO................O.O..$...O..................O.O.................O...$..................O..OO.O.....................$......O...........OOO..O...............O......$.....O.O...........OOOOOOO............O.O.....$OO...O..O................OO..........O..O...OO$OO....OO..................O...........OO....OO$.........................O....................$..............................................$..............................................$.....OO................................OO.....$.....OO................................OO.....$"
>.....OO................................OO.....
.....OO................................OO.....
..............................................
..............................................
.........................O....................
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.....O.O...........OOOOOOO............O.O.....
......O...........OOO..O...............O......
..................O..OO.O.....................
...O..................O.O.................O...
..O.O...............OO.OO................O.O..
..OO................OOOO..................OO..
..............................................
..OO................OOOO..................OO..
..O.O...............OO.OO................O.O..
...O..................O.O.................O...
..................O..OO.O.....................
......O...........OOO..O...............O......
.....O.O...........OOOOOOO............O.O.....
OO...O..O................OO..........O..O...OO
OO....OO..................O...........OO....OO
.........................O....................
..............................................
..............................................
.....OO................................OO.....
.....OO................................OO.....
</a></pre></td></tr></table></center>
<p><a name=p144gun>:</a><b>p144 gun</b> A <a href="lex_g.htm#glidergun">glider gun</a> with <a href="lex_t.htm#true">true</a> period 144. The first one was
found by Bill Gosper in July 1994. For a full description and
pattern see <a href="lex_f.htm#factory">factory</a>.
<p><a name=p14gun>:</a><b>p14 gun</b> A glider gun which emits a period 14 glider stream. This is
the smallest possible period for any stream, so such a gun is of
great interest. There is no known true-period p14 glider gun, and
finding a small direct example is well beyond current search
algorithms' abilities. However, pseudo-period p14 guns have been
created by <a href="lex_i.htm#inject">injecting</a> gliders into a higher period glider stream.
The first pseudo p14 gun was built by Dieter Leithner in 1995.
Smaller pseudo p14 guns have since been constructed, but they are
still much too large to show here. The essential mechanism used by
them is demonstrated in <a href="lex_g.htm#gig">GIG</a>.
<p><a name=p15bouncer>:</a><b>p15 bouncer</b> Noam Elkies' <a href="lex_c.htm#colourchanging">colour-changing</a> glider reflector, with
<a href="lex_k.htm#karelsp15">Karel's p15</a> providing the necessary <a href="lex_d.htm#domino">domino</a> <a href="lex_s.htm#spark">spark</a>. Compare to
the <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_s.htm#snark">Snark</a>. The minimum <a href="lex_r.htm#repeattime">repeat time</a> is 30
ticks.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:........................O..$........................O.O$........................OO.$...........................$...........................$...........................$...........................$.................O.........$................O..........$................OOO........$...........................$...OO....OO.........OO.....$..O..O..O..O....OO..OO.....$..OO......OO...O.O.........$..OO......OO....O..........$....OO..OO.................$..................OO.......$..................O........$...................OOO.....$.O..O.OO.O..O........O.....$OO..O....O..OO.............$.O..O.OO.O..O..............$"
>........................O..
........................O.O
........................OO.
...........................
...........................
...........................
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................O..........
................OOO........
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..OO......OO....O..........
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..................OO.......
..................O........
...................OOO.....
.O..O.OO.O..O........O.....
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.O..O.OO.O..O..............
</a></pre></td></tr></table></center>
<p><a name=p15bumper>:</a><b>p15 bumper</b> A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a> with
<a href="lex_k.htm#karelsp15">Karel's p15</a> providing the necessary <a href="lex_s.htm#spark">spark</a>. The minimum
<a href="lex_r.htm#repeattime">repeat time</a> is 45 ticks. For an equivalent <a href="lex_c.htm#colourchanging">colour-changing</a>
periodic glider reflector see <a href="#p15bouncer">p15 bouncer</a>. A <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a>
reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This changes the
timing of the output glider, which can be useful for rephasing
periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:............................O.O$............................OO.$.............................O.$...............................$...............................$...............................$...............................$...............................$...............................$...............................$...............................$.................O.............$.................O.O...........$.................OO............$...............................$...............OO..............$.OO.OO.OO.....O..O.............$.OO....OO......O.O.............$.OO.OO.OO.......O..............$...............................$....OO..............OO.........$..O....O............O..........$.O......O............OOO.......$O........O.............O.......$O........O.....................$O........O.....................$.O......O......................$..O....O.......................$....OO.........................$"
>............................O.O
............................OO.
.............................O.
...............................
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...............................
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...............................
.................O.............
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.................OO............
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.OO.OO.OO.....O..O.............
.OO....OO......O.O.............
.OO.OO.OO.......O..............
...............................
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.O......O......................
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....OO.........................
</a></pre></td></tr></table></center>
<p><a name=p15reflector>:</a><b>p15 reflector</b> An ambiguous term that may refer to
<a href="#pdpairreflector">PD-pair reflector</a>, <a href="#p15bouncer">p15 bouncer</a>, or the more recently discovered
<a href="#p15bumper">p15 bumper</a>.
<p><a name=p184gun>:</a><b>p184 gun</b> A <a href="lex_t.htm#true">true</a> period 184 <a href="lex_d.htm#doublebarrelled">double-barrelled</a> glider gun found by
Dave Buckingham in July 1996. The <a href="lex_e.htm#engine">engine</a> in this gun is a
<a href="lex_h.htm#herscheldescendant">Herschel descendant</a>. Unlike previous glider guns, the reaction
flips on a diagonal so that both gliders travel in the same
direction.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...................O...........$.................OOO...........$................O..............$................OO.............$..............................O$............................OOO$...........................O...$...........................OO..$...............................$...............................$...............................$...............................$....................OO.........$...................O.O.........$...................O...........$...................OO.O........$..OO.................OO........$.O.O...........................$.O.............................$OO.............................$...............................$...............................$...............................$...............................$...............................$...............................$...............................$......OO.......................$.....O.O.......................$.....O.........................$....OO.........................$"
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</a></pre></td></tr></table></center>
<p><a name=p1megacell>:</a><b>p1 megacell</b> (p1 circuitry) A <a href="lex_m.htm#metacell">metacell</a> constructed by Adam P.
Goucher in 2008, capable of being programmed to emulate any Moore
neighborhood rule, including isotropic and anisotropic non-totalistic
rules. It fits in a 32768 by 32768 bounding box, with the resulting
metacell grid at 45 degrees to the underlying Life grid. Like the
<a href="lex_o.htm#otcametapixel">OTCA metapixel</a>, it includes a large "pixel" area so that the state
of the megacell can easily be seen even at extremely small-scale zoom
levels.
<p><a name=p1telegraph>:</a><b>p1 telegraph</b> (p1 circuitry) A variant of Jason Summers' <a href="lex_t.htm#telegraph">telegraph</a>
pattern, constructed in 2010 by Adam P. Goucher using only stable
circuitry. A single incoming glider produces the entire ten-part
composite lightspeed signal that restores the beehive-chain
<a href="lex_l.htm#lightspeedwire">lightspeed wire</a> to its original position. The signal is detected
at the other end of the telegraph and converted back into a single
output signal. This simplification came at the cost of a much slower
transmission speed, one bit per 91080 ticks. In this mechanism,
sending the entire ten-part signal constitutes a '1' bit, and not
sending the signal means '0'. See also <a href="lex_h.htm#highbandwidthtelegraph">high-bandwidth telegraph</a>.
<p><a name=p22gun>:</a><b>p22 gun</b> A <a href="lex_t.htm#true">true</a> period 22 <a href="lex_g.htm#glidergun">glider gun</a> constructed by David Eppstein
in August 2000, using two interacting copies of a p22 oscillator
found earlier the same day by Jason Summers.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..................OO.........................$...................O.......O.................$...................O.O..............OO.......$....................OO............OO..O......$........................OOO.......OO.OO......$........................OO.OO.......OOO......$........................O..OO............OO..$.........................OO..............O.O.$...................................O.......O.$...........................................OO$.............................................$OO...........................................$.O...........................................$.O.O.............OOO.........................$..OO...O........O...O........................$......O.OO......O....O.......................$.....O....O......OO.O........................$......O...O........O...OO....................$.......OOO.............O.O...................$.........................O...................$.........................OO..................$"
>..................OO.........................
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.........................O...................
.........................OO..................
</a></pre></td></tr></table></center>
<p><a name=p246gun>:</a><b>p246 gun</b> A <a href="lex_t.htm#true">true</a> period <a href="lex_g.htm#glidergun">glider gun</a> with period 246, discovered by
Dave Buckingham in June 1996. The 180-degree mod-123 symmetry of its
<a href="lex_b.htm#bookend">bookend</a>-based <a href="lex_e.htm#engine">engine</a> makes it trivial to modify it into a
<a href="lex_d.htm#doublebarrelled">double-barrelled</a> gun. Its single-barreled form is shown below.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..................................O........$..................................OOO......$................................OO...O.....$...............................O.O.OO.O....$..............................O..O..O.O....$....................................O.OO...$..................................O.O......$................................O.O.O......$.................................OO.OO.....$...........................................$OO.........................................$.O.........................................$.O.O.................OO....................$..OO..................O..................OO$....................O.O..................O.$....................OO.................O.O.$.......................................OO..$...........................................$...........................................$...........................................$...........................................$...........................................$...........................................$.............................OO............$.......................O.....OO............$.................OO.OOO....................$.................O..OOOO...................$.................O.OO......................$...........................................$...........................................$.....O.....................................$....O.OOOO.................................$...O.O.OOO.................................$..O.O......................................$...O.......................................$...OO......................................$...OO......................................$...OO......................................$"
>..................................O........
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</a></pre></td></tr></table></center>
<p><a name=p24gun>:</a><b>p24 gun</b> A <a href="lex_g.htm#glidergun">glider gun</a> with <a href="lex_t.htm#true">true</a> period 24. The first one was
found by Noam Elkies in June 1997. It uses three p4 <a href="lex_o.htm#oscillator">oscillators</a> to
<a href="lex_h.htm#hassle">hassle</a> a pair of <a href="lex_t.htm#trafficlight">traffic lights</a>. One of the oscillators was very
large and custom-made. Shown below is a much smaller version built
by Jason Summers and Karel Suhajda in December 2002, using the same
mechanism but with a smaller oscillator:
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</a></pre></td></tr></table></center>
<p><a name=p256gun>:</a><b>p256 gun</b> A <a href="lex_t.htm#true">true</a> period 256 four-barrelled <a href="lex_g.htm#glidergun">glider gun</a> found by
Dave Buckingham in September 1995. It uses four <a href="lex_r.htm#r64">R64</a> <a href="lex_c.htm#conduit">conduits</a> to
make the second smallest known <a href="lex_h.htm#herschelloop">Herschel loop</a> (after the
<a href="lex_s.htm#simkinglidergun">Simkin glider gun</a>). The p256 gun was an early "teaser" from Dave
Buckingham before he released his full <a href="lex_h.htm#herschel">Herschel</a> <a href="lex_t.htm#technology">technology</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...............................OO................$...............................OO.....OO.........$......................................OO.........$.................................................$.................................................$.......OO........OO.................OO...........$.......OO.........O.................OO...........$..................O.O.....................OO.....$...................OO.....................OO.....$.OO..............................................$.OO..............................................$.....OO..........................................$.....OO...............O..........................$......................O.O........................$......................OOO........................$........................O........................$OO...............................................$OO.........................................OO....$...........................................O.....$.........................................O.O.....$.........................................OO......$.................................................$.................................................$.................................................$.................................................$.................................................$.................................................$.................................................$.................................................$.................................................$.................................................$......OO.......................................OO$......O........................................OO$.......O.........................................$......OO.........................................$......................O.O........................$.......................OO.................OO.....$.......................O..................OO.....$..............................................OO.$..............................................OO.$.....OO..........................................$.....OO..........................................$...........OO...........................OO.......$...........OO...........................OO.......$.................................................$.................................................$.........OO......................................$.........OO.....OO...............................$................OO...............................$"
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</a></pre></td></tr></table></center>
Either <a href="lex_e.htm#eater">eaters</a> or <a href="lex_s.htm#snake">snakes</a> can be added as shown above, to suppress
three of the glider streams so that only one stream escapes. This
gun's p256 glider stream is well-suited for repeated reactions with
receding <a href="lex_c.htm#cordership">Corderships</a>, or for "Hashlife-friendly" <a href="lex_s.htm#signal">signal</a>
<a href="lex_c.htm#circuit">circuitry</a>.
<p><a name=p29pentadecathlonhassler>:</a><b>p29 pentadecathlon hassler</b> A <a href="lex_h.htm#hassler">hassler</a> where two copies of a period
29 oscillator (which is itself a <a href="#prepulsar">pre-pulsar</a> hassler) change the
period of a <a href="#pentadecathlon">pentadecathlon</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..........O.......O....................O.......O..........$.........O.O.....O.O..................O.O.....O.O.........$..........O.......O....................O.......O..........$..........................................................$..........................................................$..........................................................$.........................OO....OO.........................$.........................OOO..OOO.........................$...OO....................OO....OO....................OO...$...O.......O.....O......................O.....O.......O...$OO.O......OOO...OOO....................OOO...OOO......O.OO$O..OO.....OOO...OOO....................OOO...OOO.....OO..O$.OO....O.............OO............OO.............O....OO.$...OOOOO.............O.O..........O.O.............OOOOO...$...O....OO.............O..........O.............OO....O...$....OO..O.......OO.....OO........OO.....OO.......O..OO....$......O.O.......OO......................OO.......O.O......$......O.O.O..O..............................O..O.O.O......$.......OO.OOOO..............................OOOO.OO.......$.........O......................................O.........$.........O.O..................................O.O.........$..........OO..................................OO..........$"
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</a></pre></td></tr></table></center>
<p><a name=p30gun>:</a><b>p30 gun</b> A <a href="lex_g.htm#glidergun">glider gun</a> with <a href="lex_t.htm#true">true</a> period 30. The first one, found
by Bill Gosper in November 1970 (see <a href="lex_g.htm#gosperglidergun">Gosper glider gun</a>), was also
the first gun found of any period. All known p30 glider guns are
made from two or more interacting <a href="lex_q.htm#queenbeeshuttle">queen bee shuttles</a>. Paul Callahan
found 30 different ways that three <a href="lex_q.htm#queenbeeshuttle">queen bee shuttles</a> can react to
form a period 30 glider gun. One of the most interesting of these is
shown below in which the gliders emerge in an unexpected direction.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OO...................................$.O...................................$.O.O......O.............O............$..OO......OOOO........O.O............$...........OOOO......O.O.............$...........O..O.....O..O.............$...........OOOO......O.O.............$..........OOOO........O.O........OO..$..........O.............O........O.O.$...................................O.$...................................OO$.....................................$................OOO..................$...............OO.OO.................$...............OO.OO.................$...............OOOOO.................$..............OO...OO................$.....................................$.....................................$.....................................$.....................................$.....................................$.....................................$..............OO.....................$...............O.....................$............OOO......................$............O........................$"
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</a></pre></td></tr></table></center>
<p><a name=p30reflector>:</a><b>p30 reflector</b> = <a href="lex_b.htm#buckaroo">buckaroo</a>
<p><a name=p30shuttle>:</a><b>p30 shuttle</b> = <a href="lex_q.htm#queenbeeshuttle">queen bee shuttle</a>
<p><a name=p36gun>:</a><b>p36 gun</b> A glider gun with <a href="lex_t.htm#true">true</a> period 36. The first one was found
by Jason Summers in 2004. Shown below is a smaller version using
improvements by Adam P. Goucher and Scot Ellison:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:................................................O.$..............................................OOO.$.............................................O....$.............................................OO...$..................................................$..................................................$..................................................$..................................................$..................................................$..................................................$.................................OO...............$................................O..O..............$................................O.O.O.............$.................................O..OOO...........$..................................................$...................................OO.....OO......$...................................O.....O.OO.....$.........................................O..O.....$..........................................OOO.....$......................................OO..OO......$.....................................OOO..........$.....................................O..O.........$.....................................OO.O.....O...$......................................OO.....OO...$..........................OO......................$OO.......................O..O..............OOO..O.$.O........................O.O................O.O.O$.O.O..................OO...O..................O..O$..OO..........O........O.OO....................OO.$.............OO..........O........................$............OO.O.........O........................$.............O.O..................................$..............OO..................................$.......................OO.........................$.......................O.O........................$.............O.........O.OO.......................$.............O..........OO........................$............OO.O........O.........................$...........O...OO.................................$..........O.O.....................................$..........O..O....................................$...........OO...........O...........OO............$.......................O.O...........O............$.......................O.O..OOOOOOOOO.............$....................OO.O..O.OOOOOOO..OOO..........$....................OO.O....OOOOOO..O..O..........$.......................O.............OO...........$.......................O.O....OO..................$........................OO....OO..................$"
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</a></pre></td></tr></table></center>
<p><a name=p3bumper>:</a><b>p3 bumper</b> A variant of Tanner Jacobi's <a href="lex_b.htm#bumper">bumper</a> found by Arie Paap in
April 2018. Two forms of the period 3 <a href="lex_o.htm#oscillator">oscillator</a> <a href="lex_c.htm#catalyst">catalyst</a> are
shown below.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..O........................O..................$O.O......................O.O..................$.OO.......................OO..................$......................O.......................$....................OOO.......................$...................O..........................$...................OO.........................$..................OO..........................$.......OO........OO.............OO.........OO.$......O..O....O...O............O..O....O.OOOO.$......O.O...OOO.OOO............O.O...OOO..O.O.$.......O.........O..............O.............$............OOOOOO...................OOO......$..OO........OO.O...........OO.......O.OOO.O.OO$...O.......OO...............O......O....O.OO.O$OOO......................OOO.......OO..OOO....$O........................O............O...OOO.$.......................................OOO..O.$.........................................O....$"
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</a></pre></td></tr></table></center>
<p>For bounding box optimization purposes, it's also possible to
replace the <a href="lex_e.htm#eater1">eater1</a> in a p3, p6 or p9 bumper with another period 3
oscillator, saving one row along the south edge at the cost of a
higher population.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....O.........................$..O.O.........................$...OO.........................$..............................$..............................$..............................$..............................$..............................$.............................O$......O......O.............OOO$.O...O.O...O.O............O...$O.O..O.O....OO.............O..$O.OOO.O.................O..O..$.O..OO........OO........O.....$..OOO........O..O....OOO..O...$.............O.O....OOOO.O....$....OOO.......O...............$...O..O............O..O.O.....$...OOOOO.OO...........O.......$.O.O...OO.O.......OOO.........$.OO......O....................$"
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</a></pre></td></tr></table></center>
<p>The <a href="lex_r.htm#repeattime">repeat time</a> for all these variants is 36 ticks, as shown.
<p><a name=p44gun>:</a><b>p44 gun</b> A <a href="lex_g.htm#glidergun">glider gun</a> with a <a href="lex_t.htm#true">true</a> period of 44. The first one was
found by Dave Buckingham in April 1992. It uses two interacting
copies of an <a href="lex_o.htm#oscillator">oscillator</a> which he also found. In 1996 he found a
gun which only used one copy of the oscillator. Paul Callahan
improved it in 1997, resulting in the gun shown below:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.................OO......OO.................$.................OO......OO.................$............................................$............................................$............................................$............................................$............................................$............................................$.OO......................................OO.$O.O......................................O.O$O.O.OO................................OO.O.O$.O.O.O................................O.O.O.$...O....................................O...$..O..O.............O....O.............O..O..$..O...............OO....OO...............O..$..O...O..........O........O..........O...O..$..O...O...........OO....OO...........O...O..$..O................O....O................O..$..O..O................................O..O..$...O....................................O...$.O.O.O................................O.O.O.$O.O.OO................................OO.O.O$O.O......................................O.O$.OO......................................OO.$............................................$............................................$............................................$...............OO...........................$................O...........................$.............OOO............................$.............O....................OO........$..................OO..............O.O.......$..................OO................O.......$....................................OO......$............................................$............................................$............................................$....................OO......................$...................O.O......................$...................O........................$..................OO........................$"
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</a></pre></td></tr></table></center>
<p><a name=p44mwssgun>:</a><b>p44 MWSS gun</b> A gun discovered by Dieter Leithner in April 1997, in a
somewhat larger form. This was the smallest known gliderless gun and
smallest known MWSS gun until the construction in 2017 of the gun
shown under <a href="lex_g.htm#gliderless">gliderless</a>, based on <a href="lex_t.htm#tannersp46">Tanner's p46</a>.
<p>The p44 MWSS gun is based on a p44 oscillator discovered by Dave
Buckingham in early 1992, shown here in an improved form found in
January 2005 by Jason Summers using a new p4 <a href="lex_s.htm#sparker">sparker</a> by Nicolay
Beluchenko. A glider shape appears in this gun for three consecutive
generations, but always as part of a larger <a href="lex_c.htm#cluster">cluster</a>, so even a
purist would regard this gun as gliderless.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.......O..........................................$..OO...O.O....O...................................$..O..OO..O.O.OO.O..OOO..OO........................$....OO.......OO.O.O.OO..OO........................$...OOO.......O.......OOO.........O................$.......................O.......OOO................$.......................O......O........OOO........$..............................OO.......O..O.......$.........OO..............O.............O..........$.........OO.............O..............O...O......$.........................OO............O..........$........................O.O.............O.O.......$..................................................$.......................O.O.....OOO................$........................O.....O..O..............OO$OO............OOO.......O......OO...........OO.O.O$OO...........O...O..........................OO.O..$.............OO.OO..............................O.$.................................OO.........OO.OO.$..............................OO.............O.O..$.............................................O.O..$..............................................O...$.............OO.OO.............O.O................$OO...........O...O.............OO.................$OO............OOO.................................$...........................OO.....................$...........................O.O....................$.............................O....................$.............................OO...................$..................................................$.........OO.......................................$.........OO.......................................$..................................................$.......................O..........................$.......................O..........................$...OOO.......O.......OOO..........................$....OO.......OO.O.O.OO..OO........................$..O..OO..O.O.OO.O..OOO..OO........................$..OO...O.O....O...................................$.......O..........................................$"
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..O..OO..O.O.OO.O..OOO..OO........................
..OO...O.O....O...................................
.......O..........................................
</a></pre></td></tr></table></center>
<p><a name=p45gun>:</a><b>p45 gun</b> A <a href="lex_t.htm#true">true</a>-period glider gun discovered by Matthias Merzenich
in April 2010. By most measures this is the smallest known
odd-period gun of any type, either true-period or <a href="#pseudo">pseudo</a>-period:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...............O..O..O..........................$...............OOOOOOO..........................$................................................$...............OOOOOOO..........................$...............O..O..O..........................$................................................$................................................$................................................$................................................$................................................$................O..O............................$............OO..O..O............................$............OO..O..O.......OO...................$...........................OO....OO...O..O...OO.$.................................OOOOO....OOOOO.$.................................OO...O..O...OO.$...........................OOO..................$................................................$OO.OO...........................................$.O.O.......................OOO..................$.O.O......OOO...................................$OO.OO.............................O.O...........$.O.O...............................OO...........$.O.O......OOO......................O............$OO.OO...........................................$................................................$...........OO...................................$...........OO.......O..O..OO....................$....................O..O..OO....................$....................O..O........................$................................................$................................................$...............................................O$.............................................O.O$..............................................OO$..................O..O..O.......................$..................OOOOOOO.......................$................................................$..................OOOOOOO.......................$..................O..O..O.......................$"
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..................OOOOOOO.......................
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</a></pre></td></tr></table></center>
<p><a name=p46gun>:</a><b>p46 gun</b> A glider gun which has true-period 46. The first one found
was the <a href="lex_n.htm#newgun">new gun</a> by Bill Gosper in 1971. Prior to the discovery of
<a href="lex_t.htm#tannersp46">Tanner's p46</a> in October 2017, all known p46 guns were made from two
or more <a href="lex_t.htm#twinbeesshuttle">twin bees shuttles</a> that interact (e.g., see
<a href="lex_t.htm#twinbeesshuttlepair">twin bees shuttle pair</a>). See <a href="lex_e.htm#edgeshooter">edge shooter</a> and <a href="lex_d.htm#doublebarrelled">double-barrelled</a>
for two more of these.
<p>On 21 October 2017 Heinrich Koenig found a glider gun using two
copies of <a href="lex_t.htm#tannersp46">Tanner's p46</a> placed at right angles to each other. This
is the first p46 gun found which makes no use of the
<a href="lex_t.htm#twinbeesshuttle">twin bees shuttle</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....OO.............................$.....O.............................$.....O.O...........................$......OO..OO.......................$..........OO.......................$...................................$...................................$...................................$...................................$...................................$...................................$O..................................$OOO.......OO.......................$...O......O.O......................$..O.O.......O......................$..OO......O.O......................$..........OO.......................$..OO...............................$..O................................$...OOO.............................$.....O.............................$........OO.........................$.........O.........................$......OOO..............OOO.........$......O...............O...O........$.....................O.....O.......$.............OO......O.....O.......$.............OO......OOO.OOO.......$...............................OO..$...............................O.O.$............OO...................O.$.............O...................OO$..........OOO................OO....$..........O.............O....O.....$.......................O.O.O.O.....$......................O.OO.OO......$......................O............$.....................OO............$"
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</a></pre></td></tr></table></center>
<p>See <a href="lex_g.htm#gliderless">gliderless</a> for a <a href="lex_m.htm#mwss">MWSS</a> gun also made using two copies of
Tanner's p46.
<p><a name=p46shuttle>:</a><b>p46 shuttle</b> = <a href="lex_t.htm#twinbeesshuttle">twin bees shuttle</a>
<p><a name=p48gun>:</a><b>p48 gun</b> A <a href="lex_t.htm#true">true</a> period compound <a href="lex_g.htm#glidergun">glider gun</a> based on the <a href="#p24gun">p24 gun</a>,
using a <a href="lex_r.htm#richsp16">Rich's p16</a> <a href="lex_o.htm#oscillator">oscillator</a> as a <a href="lex_f.htm#filter">filter</a> to remove half of the
gliders from the <a href="lex_s.htm#stream">stream</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.................OO...........OO.............$................O..O.........O..O............$................O.O...OO.OO...O.O............$..............OO..O.O.......O.O..OO..........$...............O.O.O....O....O.O.O...........$..............O..OO..OOOOOOO..OO..O..........$..............OO.....O.O.O.O.....OO..........$.......................O.O...................$.....O..OO.........OOO.....OOO...............$....O.O..O..O.....O.O.O...O.O.O..............$....O.OO.O.O.O....OO..OOOOO..OO..............$...OO.O..O.O..O..............................$...O..O.OO..O................................$....OOO.O.O...OOO............................$......OO.O.....OO............................$..O.O..O.O...O..O....O.O.O...................$..OO..OO.O.OO..OOO....OOO.............OO.....$........OO.O...OO......O.............O..O....$..OOOOO....O........................OO.......$.O....O.OOO.................OO.....OOO.....O.$.O.OO.O.O......OO.......O...O.O....O..O...O.O$OO.O..O......OOOO........O....O.....OOO...OO.$.O.O.O.O.....OO..O.....OOO....OO.............$.O.O.OO.O..O........................OOO...OO.$OO.OO..OO...OOOO...................O..O...O.O$...O..OOO..O..OO....O..............OOO.....O.$...O.O.OO.....O....O.O........O.....OO.......$..OO.O..OO.O..O...O...O........O.....O..O....$....O...OO..O..O...O.O.......OOO......OO.....$....O.O.......O.....O........................$...OO.OO..........OOO........................$..........OO....OOOOOOO....OO................$..........O..O..OO.O.OO..O..O................$...........OO.OOOO...OOOO.OO.................$........OOO..O...........O..OOO..............$.......O...OO.OO.......OO.OO...O.............$.......OO.O...OO.......OO...O.OO.............$........O.OOO...O.....O...OOO.O..............$.......O......OO.......OO......O..........O..$........OOOOOO...........OOOOOO............O.$..........O..O...........O..O............OOO.$"
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..........O..O...........O..O............OOO.
</a></pre></td></tr></table></center>
<p><a name=p4bumper>:</a><b>p4 bumper</b> (p4) A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a>
with a minimum <a href="lex_r.htm#repeattime">repeat time</a> of 36. Unlike the p5 through p8 cases
where Noam Elkies' <a href="lex_d.htm#domino">domino</a> spark-based reflectors are available, no
small period-4 <a href="lex_c.htm#colourchanging">colour-changing</a> reflector is known. A <a href="lex_s.htm#stable">stable</a>
<a href="lex_s.htm#snark">Snark</a> reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This changes
the timing of the output glider, which can be useful for rephasing
periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....................O..$.....................O.O$.....................OO.$........................$........................$........................$........................$........................$........................$............O...........$............O.O.........$............OO..........$........................$....OO....OO............$...O..O..O..O...........$..........O.O...........$...........O............$..O..O..................$..O.OO.........OO.......$...O.OOO.......O........$OOO...O.O.......OOO.....$O.......O.........O.....$........OO..............$"
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...O.OOO.......O........
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O.......O.........O.....
........OO..............
</a></pre></td></tr></table></center>
<p><a name=p4reflector>:</a><b>p4 reflector</b> The following <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a>, discovered by Karel
Suhajda in October 2012. Its minimum repeat time is 52 ticks.
Unlike the various <a href="lex_b.htm#bouncer">bouncers</a> discovered many years earlier, it is a
<a href="lex_c.htm#colourpreserving">colour-preserving</a> reflector, so it was made obsolete the following
year by the discovery of the much smaller stable <a href="lex_s.htm#snark">Snark</a>, which uses
the same initial <a href="lex_b.htm#bait">bait</a> reaction and so produces an output glider
with the same timing. For a smaller periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a>
glider reflector with a different output timing, see <a href="#p4bumper">p4 bumper</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:................................O.........................$...............................O..........................$...............................OOO.......O.O..............$........................................O.OO..............$......................................OOO.....O...........$.....................................O...OOOOOOOO.........$..................................O.O.O..O.......O........$..............O...................OOOO.OO.OOOOOOO.O.......$..............OOO..................OOO.....O.O..O.O..OO...$.................O...................OOO.O.O...OO.O.O.O...$................OO.............OOO..OO.OOOOO....O.O.O.....$.............................O.O...OOO.OO.O..O.OOOO..O..OO$...........................OO.....O....O..O..O...O....O..O$...................O.......OO.O.O..O......O..O....OOOOOOO.$..................O...........O.O..O..O..O.........O......$..................OOO........O....O..O...........O...OO...$............................O.OOOOOOO........OO.O.OOO.O...$.............................O.........O.O....O.O.O.......$...................OO..........OOOOOOOOO.OOO..O.O.........$...................OO.......O...O.......O...O.O.O.........$...........................O..O...OOOO..O..O.O.O..........$.............................OO...O...O.O.O..O............$.............................O.....OOO.O.O.OO..O..........$........OO...............O...OOO.....O...O...OOO..........$...OO..O..O..................O...OO..O..O.OO..............$...O....O.O..................O...OOOO...O.O.OO............$OO.O.....O................OOO...O......OO...O.O...........$.O.O.OO....................OOO.....O..OO..O.O.O...........$O..O..O........OO...........OOO..OOO.OOO..O.O.OO..........$OO..O....O.....O.O..........O..O...O...O..O.O.............$.....OOOOO.......O...........O.O..O.OO...OOOO.............$................O..........O.O.O.OOO.OOO.O................$.......O.........OOO......O.OO.O..OO......................$......O.O..........O......O.....O......OO.O...............$.......O...................OOOOO......O..OO...............$.............................O........OO..................$"
>................................O.........................
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...........................O..O...OOOO..O..O.O.O..........
.............................OO...O...O.O.O..O............
.............................O.....OOO.O.O.OO..O..........
........OO...............O...OOO.....O...O...OOO..........
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.............................O........OO..................
</a></pre></td></tr></table></center>
<p><a name=p54shuttle>:</a><b>p54 shuttle</b> (p54) A surprising variant of the <a href="lex_t.htm#twinbeesshuttle">twin bees shuttle</a>
found by Dave Buckingham in 1973. See also <a href="lex_c.htm#centinal">centinal</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt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</a></pre></td></tr></table></center>
<p><a name=p5bouncer>:</a><b>p5 bouncer</b> (p5) A <a href="lex_c.htm#colourchanging">colour-changing</a> glider reflector constructed by
Noam Elkies in September 1998 by welding together two special-purpose
period-5 <a href="lex_s.htm#sparker">sparkers</a>. The minimum <a href="lex_r.htm#repeattime">repeat time</a> is 25 ticks. For
<a href="lex_c.htm#colourpreserving">colour-preserving</a> glider reflectors see <a href="#p5bumper">p5 bumper</a> and the
<a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a> reflector.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..........................O..$........................OO...$.........................OO..$.............................$.............................$........OO...................$.....O..O.O........O.........$....O.O.O.O.......O..........$...O.O.O..OO......OOO........$...O...O.O..O................$OO.OO..O.O.O..........OO.....$O.O....OOO..O.....OO..OO.....$..O.OOO...OO.....O.O.........$..O..O.....O......O..........$...O...O.O..O............OO..$....OOO.OO.OO.......OO....O..$......O....O........OO..OOO..$.......OOO.O.....OO.....OOO..$..........O.OO...OO.....OO...$.........O..O..OOO.O........O$.........OO..OOO...........OO$................O............$.............OOOO.O..........$............O..O...O.........$............OO...O.OOO.......$.............O.O..O...O......$.............O.OO.O..OO......$..............O..O...........$...............OO............$"
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</a></pre></td></tr></table></center>
<p><a name=p5bumper>:</a><b>p5 bumper</b> A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a> with a
<a href="lex_m.htm#middleweightvolcano">middleweight volcano</a> producing the necessary <a href="lex_s.htm#spark">spark</a>. The minimum
<a href="lex_r.htm#repeattime">repeat time</a> is 35 ticks. For an equivalent <a href="lex_c.htm#colourchanging">colour-changing</a>
periodic glider reflector see <a href="#p5bouncer">p5 bouncer</a>. A <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a>
reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This changes the
timing of the output glider, which can be useful for rephasing
periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:............................O$..........................OO.$...........................OO$.............................$.............................$.............................$.............................$.............................$.............................$...OO..O..........O..........$...O..O.O.........O.O........$....O.O.O.........OO.........$...OO.O.OO...................$..O...OO..O.....OO...........$.O..OO...OOO...O..O..........$.O.O.OO..OOO....O.O..........$..O.OO...OOO.....O...........$......OO..O..................$OOOOO.O.OO...........OO......$O..O..O.O............O.......$.....O..O.............OOO....$......OO................O....$"
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</a></pre></td></tr></table></center>
<p><a name=p5reflector>:</a><b>p5 reflector</b> Traditional name for <a href="#p5bouncer">p5 bouncer</a> before 2016, but with
the discovery of the <a href="#p5bumper">p5 bumper</a> this has become an ambiguous
reference.
<p><a name=p60gun>:</a><b>p60 gun</b> A glider gun with a <a href="lex_t.htm#true">true</a> period of 60. The first one was
found by Bill Gosper in 1970 and is shown below.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:............................O..........$............................O.O........$...........OO..................OO......$.........O...O.................OO....OO$...OO...O.....O................OO....OO$...OO..OO.O...O.............O.O........$........O.....O.............O..........$.........O...O.........................$...........OO..........................$.......................................$.......................................$.......................................$.......................................$.......................................$.......................................$.......................................$..........O.O..........................$.........O..O...OO.....................$OO......OO.....OOO.OO..OO..............$OO....OO...O...O...O...O.O.............$........OO.....O.O........O............$.........O..O..OO......O..O............$..........O.O.............O............$.......................O.O.......OO....$.......................OO........O.O...$...................................O...$...................................OO..$"
>............................O..........
............................O.O........
...........OO..................OO......
.........O...O.................OO....OO
...OO...O.....O................OO....OO
...OO..OO.O...O.............O.O........
........O.....O.............O..........
.........O...O.........................
...........OO..........................
.......................................
.......................................
.......................................
.......................................
.......................................
.......................................
.......................................
..........O.O..........................
.........O..O...OO.....................
OO......OO.....OOO.OO..OO..............
OO....OO...O...O...O...O.O.............
........OO.....O.O........O............
.........O..O..OO......O..O............
..........O.O.............O............
.......................O.O.......OO....
.......................OO........O.O...
...................................O...
...................................OO..
</a></pre></td></tr></table></center>
There are several other ways to create a p60 gun from two p30 guns
using period-doubling reactions similar to the one shown here.
<p><a name=p690gun>:</a><b>p690 gun</b> A <a href="lex_t.htm#true">true</a> period 690 <a href="lex_g.htm#glider">glider</a> gun found by Noam Elkies in
July 1996. It is composed of a p30 <a href="lex_q.htm#queenbeeshuttlepair">queen bee shuttle pair</a> and a
p46 <a href="lex_t.htm#twinbeesshuttle">twin bees shuttle</a> whose sparks occasionally react with each
other. This is a very compact gun for such a high period and is used
in many patterns requiring sparse glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...........O........................................$...........OOO......................................$..............O.....................................$.............OO.....................................$....................................................$....................................................$....................................................$....................................................$...............OOO..................................$..............O...O.................................$....................................................$.............O.....O................................$.............OO...OO................................$....................................................$..........................................OO.O......$................O......OO............OOO..OO..O.....$OO.............O.O.....OO.............OO......O...OO$.O.............O.O.....................OOO...OOOO..O$.O.O.....O.....O........................O...O...OOO.$..OO...O.O.....O........O.....O.....................$......O.O......O..O.....O.....O.........O...O...OOO.$.....O..O......O..O....................OOO...OOOO..O$......O.O.......OO..OO...........OO...OO......O...OO$.......O.O...........................OOO..OO..O.....$.........O..............O.....O...........OO.O......$........................O.....O.....................$"
>...........O........................................
...........OOO......................................
..............O.....................................
.............OO.....................................
....................................................
....................................................
....................................................
....................................................
...............OOO..................................
..............O...O.................................
....................................................
.............O.....O................................
.............OO...OO................................
....................................................
..........................................OO.O......
................O......OO............OOO..OO..O.....
OO.............O.O.....OO.............OO......O...OO
.O.............O.O.....................OOO...OOOO..O
.O.O.....O.....O........................O...O...OOO.
..OO...O.O.....O........O.....O.....................
......O.O......O..O.....O.....O.........O...O...OOO.
.....O..O......O..O....................OOO...OOOO..O
......O.O.......OO..OO...........OO...OO......O...OO
.......O.O...........................OOO..OO..O.....
.........O..............O.....O...........OO.O......
........................O.....O.....................
</a></pre></td></tr></table></center>
<p><a name=p6bouncer>:</a><b>p6 bouncer</b> (p6) Noam Elkies' <a href="lex_c.htm#colourchanging">colour-changing</a> glider reflector using
the <a href="#p6pipsquirter">p6 pipsquirter</a>, with a minimum <a href="lex_r.htm#repeattime">repeat time</a> of 24 ticks. For
<a href="lex_c.htm#colourpreserving">colour-preserving</a> glider reflectors see <a href="#p6bumper">p6 bumper</a> and the
<a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a> reflector.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.......................O.$......................O..$......................OOO$...OO....................$...O.....................$.....O...................$....OOOO.........O.......$...O....O.......O........$...OOOOO.O......OOO......$.OO....O.O...............$O..O.....OO.........OO...$OO.O.O.O..O.....OO..OO...$...O..O.OOO....O.O.......$...OO.O...O.....O........$.....O.O.OO..............$.....O.O.O........OO.....$......O..O........O......$.......OO..........OOO...$.....................O...$"
>.......................O.
......................O..
......................OOO
...OO....................
...O.....................
.....O...................
....OOOO.........O.......
...O....O.......O........
...OOOOO.O......OOO......
.OO....O.O...............
O..O.....OO.........OO...
OO.O.O.O..O.....OO..OO...
...O..O.OOO....O.O.......
...OO.O...O.....O........
.....O.O.OO..............
.....O.O.O........OO.....
......O..O........O......
.......OO..........OOO...
.....................O...
</a></pre></td></tr></table></center>
<p><a name=p6bumper>:</a><b>p6 bumper</b> (p6) A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a>
with a <a href="lex_u.htm#unix">unix</a> providing the necessary <a href="lex_s.htm#spark">spark</a>. The minimum
<a href="lex_r.htm#repeattime">repeat time</a> is 36 ticks. For an equivalent <a href="lex_c.htm#colourchanging">colour-changing</a>
periodic glider reflector see <a href="#p6bouncer">p6 bouncer</a>. A <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a>
reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This changes the
timing of the output glider, which can be useful for rephasing
periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.......................O..$.......................O.O$.......................OO.$..........................$..........................$..........................$..........................$..........................$..........................$..............O...........$..............O.O.........$..............OO..........$..........................$............OO............$.....OO....O..O...........$.....OO.....O.O...........$.............O............$..........................$.....OOO.........OO.......$OO..O.OO.........O........$OO..OO............OOO.....$....OO..............O.....$"
>.......................O..
.......................O.O
.......................OO.
..........................
..........................
..........................
..........................
..........................
..........................
..............O...........
..............O.O.........
..............OO..........
..........................
............OO............
.....OO....O..O...........
.....OO.....O.O...........
.............O............
..........................
.....OOO.........OO.......
OO..O.OO.........O........
OO..OO............OOO.....
....OO..............O.....
</a></pre></td></tr></table></center>
<p><a name=p6pipsquirter>:</a><b>p6 pipsquirter</b> (p6) A <a href="#pipsquirter">pipsquirter</a> oscillator found by Noam Elkies
in November 1997, used in various <a href="lex_h.htm#hassler">hasslers</a> and the colour-changing
<a href="#p6bouncer">p6 bouncer</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....O.........$.....O.........$...............$...O...O.......$.OOO.O.OOO.....$O...OO....O....$O.OO..OO.O.O...$.O..OO..OO.O...$..OO..OO.O.O.OO$....O..O.O.O.OO$....OOOO.OO....$........O......$......O.O......$......OO.......$"
>.....O.........
.....O.........
...............
...O...O.......
.OOO.O.OOO.....
O...OO....O....
O.OO..OO.O.O...
.O..OO..OO.O...
..OO..OO.O.O.OO
....O..O.O.O.OO
....OOOO.OO....
........O......
......O.O......
......OO.......
</a></pre></td></tr></table></center>
<p><a name=p6reflector>:</a><b>p6 reflector</b> Traditional name for <a href="#p6bouncer">p6 bouncer</a> before 2016, but with
the discovery of the <a href="#p6bumper">p6 bumper</a> this has become an ambiguous
reference.
<p><a name=p6shuttle>:</a><b>p6 shuttle</b> (p6) The following oscillator found by Nicolay Beluchenko
in February 2004.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:O.............$OOO...........$...O..........$..OO..........$..............$......O.......$.....OOOO.....$......O..O....$.......OOO....$..............$..........OO..$..........O...$...........OOO$.............O$"
>O.............
OOO...........
...O..........
..OO..........
..............
......O.......
.....OOOO.....
......O..O....
.......OOO....
..............
..........OO..
..........O...
...........OOO
.............O
</a></pre></td></tr></table></center>
This is <a href="lex_e.htm#extensible">extensible</a> in more than one way:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:O........................$OOO......................$...O.....................$..OO.....................$.........................$......O..................$.....OOOO................$......O..O...............$.......OOO...............$.........................$..........OOO............$..........O..O...........$...........OOOO..........$.............O...........$.........................$.................O.......$................OOO......$.................O.O.....$.................O.O.....$..................OO.....$.....................OO..$.....................O.O.$.......................O.$.......................OO$"
>O........................
OOO......................
...O.....................
..OO.....................
.........................
......O..................
.....OOOO................
......O..O...............
.......OOO...............
.........................
..........OOO............
..........O..O...........
...........OOOO..........
.............O...........
.........................
.................O.......
................OOO......
.................O.O.....
.................O.O.....
..................OO.....
.....................OO..
.....................O.O.
.......................O.
.......................OO
</a></pre></td></tr></table></center>
<p><a name=p72quasishuttle>:</a><b>p72 quasi-shuttle</b> (p72) The following <a href="lex_o.htm#oscillator">oscillator</a>, found by Jason
Summers in August 2005. Although this looks at first sight like a
<a href="lex_s.htm#shuttle">shuttle</a>, it isn't really.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..............................O......$.............................OO......$............................O.OO.....$.OOOO......................OOO..O....$O....O.......................O.O.O...$O...O.O.......................O.O.O..$.O...O.O......OO...............O..OOO$.......O.....O.O................OO.O.$.......O.....O...................OO..$....O..O.....OOO.................O...$.....OO..............................$.....................................$.....OO..............................$....O..O.....OOO.................O...$.......O.....O...................OO..$.......O.....O.O................OO.O.$.O...O.O......OO...............O..OOO$O...O.O.......................O.O.O..$O....O.......................O.O.O...$.OOOO......................OOO..O....$............................O.OO.....$.............................OO......$..............................O......$"
>..............................O......
.............................OO......
............................O.OO.....
.OOOO......................OOO..O....
O....O.......................O.O.O...
O...O.O.......................O.O.O..
.O...O.O......OO...............O..OOO
.......O.....O.O................OO.O.
.......O.....O...................OO..
....O..O.....OOO.................O...
.....OO..............................
.....................................
.....OO..............................
....O..O.....OOO.................O...
.......O.....O...................OO..
.......O.....O.O................OO.O.
.O...O.O......OO...............O..OOO
O...O.O.......................O.O.O..
O....O.......................O.O.O...
.OOOO......................OOO..O....
............................O.OO.....
.............................OO......
..............................O......
</a></pre></td></tr></table></center>
<p><a name=p7bouncer>:</a><b>p7 bouncer</b> (p7) Noam Elkies' <a href="lex_c.htm#colourchanging">colour-changing</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a>
using a <a href="#p7pipsquirter">p7 pipsquirter</a>, with a minimum <a href="lex_r.htm#repeattime">repeat time</a> of 28 ticks.
A high-<a href="lex_c.htm#clearance">clearance</a> version is shown in <a href="#p7pipsquirter">p7 pipsquirter</a>. For
<a href="lex_c.htm#colourpreserving">colour-preserving</a> glider reflectors see <a href="#p7bumper">p7 bumper</a> and the
<a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a> reflector.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.......................O.$......................O..$......................OOO$.........................$.........................$.........................$.........................$................O........$......OO.......O.........$......O.O......OOO.......$........O................$...O..O.OO.........OO....$...OOOO..O.....OO..OO....$.......OOO....O.O........$...OOOO..O.....O.........$..O...O.OO...............$.O.OOOO.O........OO......$.O.O..O.O........O.......$OO.O.O.O.OO.......OOO....$O..OOO.O..O.........O....$..O...O.O................$...OO.O.OO...............$....O....................$..O.O.OOOO...............$.O.OOOO..O...............$.O.....O.................$..OOOOOO.O...............$....O...O.O..............$.......O..O..............$........OO...............$"
>.......................O.
......................O..
......................OOO
.........................
.........................
.........................
.........................
................O........
......OO.......O.........
......O.O......OOO.......
........O................
...O..O.OO.........OO....
...OOOO..O.....OO..OO....
.......OOO....O.O........
...OOOO..O.....O.........
..O...O.OO...............
.O.OOOO.O........OO......
.O.O..O.O........O.......
OO.O.O.O.OO.......OOO....
O..OOO.O..O.........O....
..O...O.O................
...OO.O.OO...............
....O....................
..O.O.OOOO...............
.O.OOOO..O...............
.O.....O.................
..OOOOOO.O...............
....O...O.O..............
.......O..O..............
........OO...............
</a></pre></td></tr></table></center>
<p><a name=p7bumper>:</a><b>p7 bumper</b> (p7) A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a>
with a minimum <a href="lex_r.htm#repeattime">repeat time</a> of 35 ticks. For an equivalent
<a href="lex_c.htm#colourchanging">colour-changing</a> periodic glider reflector see <a href="#p7bouncer">p7 bouncer</a>. A
<a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a> reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This
changes the timing of the output glider, which can be useful for
rephasing periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:......O..................$....O.O.......OO.....OO..$.....OO......O..O...O..O.$.........................$.......OO.......O...O....$......O..O....O.......O..$......O.O.....OO.....OO..$.......O.........O.O.....$.............O..OO.OO..O.$..OO........O.O..O.O..O.O$...O........O..O.O.O.O..O$OOO.............O...O....$O........................$"
>......O..................
....O.O.......OO.....OO..
.....OO......O..O...O..O.
.........................
.......OO.......O...O....
......O..O....O.......O..
......O.O.....OO.....OO..
.......O.........O.O.....
.............O..OO.OO..O.
..OO........O.O..O.O..O.O
...O........O..O.O.O.O..O
OOO.............O...O....
O........................
</a></pre></td></tr></table></center>
<p><a name=p7pipsquirter>:</a><b>p7 pipsquirter</b> A <a href="#pipsquirter">pipsquirter</a> oscillator found by Noam Elkies in
August 1999, used in various <a href="lex_h.htm#hassler">hasslers</a> and the colour-changing
<a href="#p7reflector">p7 reflector</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:................O.....$........O.......O.....$.OO...OOO..O..........$..O..O...OOO..O...O.OO$..O.O.OO....OOO.O.OO.O$OO..O.O.OOOO....O.....$.O.OO........OOO.OOOO.$.O....O.O.OO...O.O..O.$OO.O.O.OO....O.O......$.O.O......OOOO.O......$.O..OOOOOO....O.......$OO....O..O..O.........$............OO........$"
>................O.....
........O.......O.....
.OO...OOO..O..........
..O..O...OOO..O...O.OO
..O.O.OO....OOO.O.OO.O
OO..O.O.OOOO....O.....
.O.OO........OOO.OOOO.
.O....O.O.OO...O.O..O.
OO.O.O.OO....O.O......
.O.O......OOOO.O......
.O..OOOOOO....O.......
OO....O..O..O.........
............OO........
</a></pre></td></tr></table></center>
<p>A larger period-7 pipsquirter is used in cases where space is
limited where the reflector should extend southward for as short a
distance as possible:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....OO..................................$......OOO................................$....O....O...............................$..OOOOOO.O.............................O.$.O.....O.OO....OO.....................O..$.O.OO.O....O..O.O.....................OOO$..O...O.OO.O..O..........................$....O.O..O.OO.O..........................$...OO...O.....OO.........................$..O..OO.O.OOOO..O...OO...................$O..O...O.O...O.O...O.O..........O........$OO.O...O..OO.O..OOOO..OO.......O.........$.O.O.OO.O.O.O.O.O...OO..O......OOO.......$O..OOO..O.....O....O..O.O................$O.O...O.OO...OO....O.OO.OO.........OO....$.O.OOOO..O..O.O....O.....O.....OO..OO....$...O...O......OO...O..OOOO....O.O........$...O.OO..O..O.O....O.....O.....O.........$....O.O.OO...OO....O.OO.OO...............$......O.O.....O....O..O.O........OO......$......O.O...O.O.O...OO..O........O.......$.......O...O.O..OOOO..OO..........OOO....$...........O.O.O...O.O..............O....$............OO.OO...OO...................$"
>.....OO..................................
......OOO................................
....O....O...............................
..OOOOOO.O.............................O.
.O.....O.OO....OO.....................O..
.O.OO.O....O..O.O.....................OOO
..O...O.OO.O..O..........................
....O.O..O.OO.O..........................
...OO...O.....OO.........................
..O..OO.O.OOOO..O...OO...................
O..O...O.O...O.O...O.O..........O........
OO.O...O..OO.O..OOOO..OO.......O.........
.O.O.OO.O.O.O.O.O...OO..O......OOO.......
O..OOO..O.....O....O..O.O................
O.O...O.OO...OO....O.OO.OO.........OO....
.O.OOOO..O..O.O....O.....O.....OO..OO....
...O...O......OO...O..OOOO....O.O........
...O.OO..O..O.O....O.....O.....O.........
....O.O.OO...OO....O.OO.OO...............
......O.O.....O....O..O.O........OO......
......O.O...O.O.O...OO..O........O.......
.......O...O.O..OOOO..OO..........OOO....
...........O.O.O...O.O..............O....
............OO.OO...OO...................
</a></pre></td></tr></table></center>
<p><a name=p7reflector>:</a><b>p7 reflector</b> Traditional name for <a href="#p7bouncer">p7 bouncer</a> before 2016, but with
the discovery of the <a href="#p7bumper">p7 bumper</a> this has become an ambiguous
reference.
<p><a name=p8bouncer>:</a><b>p8 bouncer</b> A glider <a href="lex_r.htm#reflector">reflector</a> constructed by Noam Elkies in
September 1998, with a minimum <a href="lex_r.htm#repeattime">repeat time</a> of 24 ticks. It is a
<a href="lex_c.htm#constellation">constellation</a> containing a <a href="lex_f.htm#figure8">figure-8</a>, <a href="lex_b.htm#boat">boat</a>, <a href="lex_e.htm#eater1">eater1</a>, and
<a href="lex_b.htm#block">block</a>. For <a href="lex_c.htm#colourpreserving">colour-preserving</a> glider reflectors see <a href="#p8bumper">p8 bumper</a>
and the <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a> reflector.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:................O.$...............O..$...............OOO$..................$..................$..................$..........O.......$.........O........$.........OOO......$..................$.............OO...$.........OO..OO...$........O.O.......$.........O........$.....O............$....O.O....OO.....$...O...O...O......$..O...O.....OOO...$.O...O........O...$O...O.............$.O.O..............$..O...............$"
>................O.
...............O..
...............OOO
..................
..................
..................
..........O.......
.........O........
.........OOO......
..................
.............OO...
.........OO..OO...
........O.O.......
.........O........
.....O............
....O.O....OO.....
...O...O...O......
..O...O.....OOO...
.O...O........O...
O...O.............
.O.O..............
..O...............
</a></pre></td></tr></table></center>
<p><a name=p8bumper>:</a><b>p8 bumper</b> A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a> with a
<a href="lex_b.htm#blocker">blocker</a> attached to provide the necessary spark. The minimum
<a href="lex_r.htm#repeattime">repeat time</a> is 40 ticks. For an equivalent <a href="lex_c.htm#colourchanging">colour-changing</a>
periodic glider reflector see <a href="#p8bouncer">p8 bouncer</a>. A <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a>
reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This changes the
timing of the output glider, which can be useful for rephasing
periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....................O..$....................O.O$....................OO.$.......................$.......................$.......................$.......................$.......................$.......................$.......................$..........O............$..........O.O..........$..........OO...........$.......................$........OO.............$.OO....O..O............$.OO.....O.O............$.OO......O.............$..O....................$.O.O.........OO........$OO.O.........O.........$..............OOO......$................O......$.OO....................$.OO....................$"
>....................O..
....................O.O
....................OO.
.......................
.......................
.......................
.......................
.......................
.......................
.......................
..........O............
..........O.O..........
..........OO...........
.......................
........OO.............
.OO....O..O............
.OO.....O.O............
.OO......O.............
..O....................
.O.O.........OO........
OO.O.........O.........
..............OOO......
................O......
.OO....................
.OO....................
</a></pre></td></tr></table></center>
<p><a name=p8gtoh>:</a><b>p8 G-to-H</b> A small periodic variant of a stable two-glider-to-Herschel
component found by Paul Callahan in November 1998 and used in the
<a href="lex_c.htm#callahangtoh">Callahan G-to-H</a>, <a href="lex_s.htm#silverreflector">Silver reflector</a> and <a href="lex_s.htm#silvergtoh">Silver G-to-H</a>. The
minimum <a href="lex_r.htm#repeattime">repeat time</a> is 192 ticks, though some lower periods such as
96 are possible via <a href="lex_o.htm#overclocking">overclocking</a>. Here a <a href="lex_g.htm#ghostherschel">ghost Herschel</a> marks
the output signal location:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....O.........O...................$....OOO.....OOO...................$.......O...O......................$..O...OO...OO.....................$...O..............................$.OOO..............................$..................................$..................................$..................................$...............................O..$...............................O..$....................OO.........OOO$....................OO...........O$........OO........................$.......O..O.......................$..OO....OO........................$.O.O..............................$.O................................$OO................................$..........OO......................$..........O.......................$...........OOO....................$.............O...........OO.......$.....................OO..OO.......$....................O.O...........$.....................O............$.................O................$................O.O....OO.........$...............O...O...O..........$..............O...O.....OOO.......$.............O...O........O.......$............O...O.................$.............O.O..................$..............O...................$"
>....O.........O...................
....OOO.....OOO...................
.......O...O......................
..O...OO...OO.....................
...O..............................
.OOO..............................
..................................
..................................
..................................
...............................O..
...............................O..
....................OO.........OOO
....................OO...........O
........OO........................
.......O..O.......................
..OO....OO........................
.O.O..............................
.O................................
OO................................
..........OO......................
..........O.......................
...........OOO....................
.............O...........OO.......
.....................OO..OO.......
....................O.O...........
.....................O............
.................O................
................O.O....OO.........
...............O...O...O..........
..............O...O.....OOO.......
.............O...O........O.......
............O...O.................
.............O.O..................
..............O...................
</a></pre></td></tr></table></center>
<p><a name=p8reflector>:</a><b>p8 reflector</b> Traditional name for <a href="#p8bouncer">p8 bouncer</a> before 2016, but with
the discovery of the <a href="#p8bumper">p8 bumper</a> this has become an ambiguous
reference.
<p><a name=p90gun>:</a><b>p90 gun</b> A glider gun with <a href="lex_t.htm#true">true</a> period 90. The one below by Dean
Hickerson uses the output of two p30 guns in a period-multiplying
reaction:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:......................................O.........................$......................................OOOO......................$................................OO.....OOOO.......O.............$...........................O...O..O....O..O......O.O............$..........................O.O...OO.....OOOO....OO...O...........$.........OO...............OO.O........OOOO.....OO...O.........OO$.........O.O..............OO.OO.......O........OO...O.........OO$....OO......O.............OO.O...................O.O............$OO.O..O..O..O.............O.O.....................O.............$OO..OO......O........O.....O...........O.O......................$.........O.O.......O.O.................OO.......................$.........OO.........OO..................O.......................$................................................................$................................................................$...........................................OO...................$...........................................OO...................$................................................................$................................................................$................................................................$................................................................$................................................................$................................................................$........................................OO......................$........................................O.......................$.........................................OOO....................$...........................................O....................$"
>......................................O.........................
......................................OOOO......................
................................OO.....OOOO.......O.............
...........................O...O..O....O..O......O.O............
..........................O.O...OO.....OOOO....OO...O...........
.........OO...............OO.O........OOOO.....OO...O.........OO
.........O.O..............OO.OO.......O........OO...O.........OO
....OO......O.............OO.O...................O.O............
OO.O..O..O..O.............O.O.....................O.............
OO..OO......O........O.....O...........O.O......................
.........O.O.......O.O.................OO.......................
.........OO.........OO..................O.......................
................................................................
................................................................
...........................................OO...................
...........................................OO...................
................................................................
................................................................
................................................................
................................................................
................................................................
................................................................
........................................OO......................
........................................O.......................
.........................................OOO....................
...........................................O....................
</a></pre></td></tr></table></center>
<p><a name=p92gun>:</a><b>p92 gun</b> A glider gun with a <a href="lex_t.htm#true">true</a> period of 92. The first one was
found by Bill Gosper in 1971 using a period doubling reaction using
two p46 guns. Many different p92 guns are known that use multiple
<a href="lex_t.htm#twinbeesshuttle">twin bees shuttles</a>. A period 92 gun can also be made by adding a
<a href="lex_s.htm#semicenark">semi-cenark</a> to any period 46 glider gun.
<p>On 18 November 2017, Martin Grant found a new gun using one twin
bees shuttle and one <a href="lex_t.htm#tannersp46">Tanner's p46</a> oscillator, making it the
smallest known p92 gun.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....OO..............O.........................$.....O.............O.O........................$.....O.O...........O.O........................$......OO..OO.....OOO.OO....................OO.$..........OO....O..........................OO.$.................OOO.OO........O..............$...................O.OO....OO..O..............$.......OO.O.O.............O.....O...........OO$.......OO.O.O............OO..O.O............OO$.......OO...O.............OO...O..............$.......OO....OO......OO....OOO................$O......OO.....OO.....OO.......................$OOO.......OOO.O............OOO................$...O.....OO...O.O.O.......OO...O..............$..O.O......O..O...O......OO..O.O............OO$..OO.......O.O..O.O.......O.....O...........OO$...........................OO..O..............$..OO...........................O..............$..O........................................OO.$....O......................................OO.$...OO.........................................$........OO....................................$.........O.....................O..............$......OOO.......................O.............$......O.......................OOO.............$"
>....OO..............O.........................
.....O.............O.O........................
.....O.O...........O.O........................
......OO..OO.....OOO.OO....................OO.
..........OO....O..........................OO.
.................OOO.OO........O..............
...................O.OO....OO..O..............
.......OO.O.O.............O.....O...........OO
.......OO.O.O............OO..O.O............OO
.......OO...O.............OO...O..............
.......OO....OO......OO....OOO................
O......OO.....OO.....OO.......................
OOO.......OOO.O............OOO................
...O.....OO...O.O.O.......OO...O..............
..O.O......O..O...O......OO..O.O............OO
..OO.......O.O..O.O.......O.....O...........OO
...........................OO..O..............
..OO...........................O..............
..O........................................OO.
....O......................................OO.
...OO.........................................
........OO....................................
.........O.....................O..............
......OOO.......................O.............
......O.......................OOO.............
</a></pre></td></tr></table></center>
<p><a name=p9bumper>:</a><b>p9 bumper</b> A periodic <a href="lex_c.htm#colourpreserving">colour-preserving</a> <a href="lex_g.htm#glider">glider</a> <a href="lex_r.htm#reflector">reflector</a> with a
<a href="lex_r.htm#repeattime">repeat time</a> of 36. Unlike the p5 through p8 cases where Noam
Elkies' <a href="lex_d.htm#domino">domino</a> spark-based reflectors are available, no small
period-9 <a href="lex_c.htm#colourchanging">colour-changing</a> reflector is known. A <a href="lex_s.htm#stable">stable</a> <a href="lex_s.htm#snark">Snark</a>
reflector can be substituted for any <a href="lex_b.htm#bumper">bumper</a>. This changes the
timing of the output glider, which can be useful for rephasing
periodic glider streams.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:........................O..$........................O.O$........................OO.$...........................$...........................$...........................$...........................$...........................$...........................$...............O...........$......OO.......O.O.........$.....O.O.......OO..........$.OO..O.....................$.O.O.OO......OO............$...O...O....O..O...........$O..O.O.OO....O.O...........$OOO..O.O......O............$...OO.O....................$..O..O..O.........OO.......$...OOOOOO.........O........$...................OOO.....$.....OO..............O.....$.....OO....................$"
>........................O..
........................O.O
........................OO.
...........................
...........................
...........................
...........................
...........................
...........................
...............O...........
......OO.......O.O.........
.....O.O.......OO..........
.OO..O.....................
.O.O.OO......OO............
...O...O....O..O...........
O..O.O.OO....O.O...........
OOO..O.O......O............
...OO.O....................
..O..O..O.........OO.......
...OOOOOO.........O........
...................OOO.....
.....OO..............O.....
.....OO....................
</a></pre></td></tr></table></center>
<p><a name=pairofbookends>:</a><b>pair of bookends</b> = <a href="lex_b.htm#bookends">bookends</a>
<p><a name=pairoftables>:</a><b>pair of tables</b> = <a href="lex_t.htm#tableontable">table on table</a>
<p><a name=paperclip>:</a><b>paperclip</b> (p1) A relatively 180-degree rotationally <a href="lex_s.htm#symmetric">symmetric</a>
14-<a href="lex_b.htm#bit">bit</a> <a href="lex_s.htm#stilllife">still life</a>. The <a href="lex_i.htm#iwona">Iwona</a> <a href="lex_m.htm#methuselah">methuselah</a> contains a paperclip
in its <a href="lex_a.htm#ash">ash</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..OO.$.O..O$.O.OO$OO.O.$O..O.$.OO..$"
>..OO.
.O..O
.O.OO
OO.O.
O..O.
.OO..
</a></pre></td></tr></table></center>
<p><a name=parallelgreyship>:</a><b>parallel grey ship</b> = <a href="lex_w.htm#withthegraingreyship">with-the-grain grey ship</a>
<p><a name=parallelhbk>:</a><b>Parallel HBK</b> ((6,3)<i>c</i>/245912, p245912) A much smaller successor to the
<a href="lex_h.htm#halfbakedknightship">half-baked knightship</a>, constructed by Chris Cain in September 2014.
Several slow-salvo recipes are needed to support the multi-glider
salvo <a href="lex_s.htm#seed">seeds</a> at the upstream end of the spaceship. "Parallel" means
that these recipes are sent in parallel instead of one after the
other, in series, as in the original HBK.
<p><a name=parallelhbkgun>:</a><b>Parallel HBK gun</b> An <a href="lex_a.htm#armless">armless</a> constructor pattern that is programmed
to build <a href="#parallelhbk">Parallel HBK</a> oblique spaceships every 125906944 ticks.
This gun was created by Chris Cain on 3 January 2015.
<p><a name=parasite>:</a><b>parasite</b> A self-sustaining reaction attached to the output of a rake
or puffer, that damages or modifies the standard output. Compare
<a href="lex_t.htm#tagalong">tagalong</a>. In 2009, while experimenting with <a href="lex_n.htm#noveltygenerator">novelty generator</a>
patterns in <a href="lex_g.htm#golly">Golly</a>, Mitchell Riley discovered parasites on glider
streams from p20 and p8 backward rakes. In some cases, parasites can
even "reproduce", as in the pattern below, though the number of
copies is limited since they will eventually use up their host glider
stream:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:......O.............O.........$.....OOO...........OOO........$...OO.OOO.........OOO.OO......$....O..O.OO.....OO.O..O.......$.OO.O....O.O...O.O....O.OO....$.OO.O.O..O.OO.OO.O..O.O.OO....$.O........O.O.O.O........O....$OO.......OO.O.O.OO.......OO...$............O.O...............$.......OOO.O...O.OOO..........$......OO...........OO.........$......O.....O....OO..O........$.....OO....OOO...OO..O........$...........O.OO...OOO.........$............OOO....O..........$............OOO...............$............OOO...............$............OO................$..............................$...................O.O........$....................OO........$...............OO...O.........$........OO......OO............$.......OO......O..............$.........O....................$..............................$..............................$.................OO...........$..........O......OOO..........$.........OOO.O...OOO..........$........OO.O.....OOO..........$........OO......O.OO..........$........OO......OOO....OO.....$........OO.OO....O.....O......$.........OO...........OO......$..........OOO.O...O.OOO.......$...............O.O............$...OO.......OO.O.O.OO.......OO$....O........O.O.O.O........O.$....OO.O.O..O.OO.OO.O..O.O.OO.$....OO.O....O.O...O.O....O.OO.$.......O..O.OO.....OO.O..O....$......OO.OOO.........OOO.OO...$........OOO...........OOO.....$.........O.............O......$"
>......O.............O.........
.....OOO...........OOO........
...OO.OOO.........OOO.OO......
....O..O.OO.....OO.O..O.......
.OO.O....O.O...O.O....O.OO....
.OO.O.O..O.OO.OO.O..O.O.OO....
.O........O.O.O.O........O....
OO.......OO.O.O.OO.......OO...
............O.O...............
.......OOO.O...O.OOO..........
......OO...........OO.........
......O.....O....OO..O........
.....OO....OOO...OO..O........
...........O.OO...OOO.........
............OOO....O..........
............OOO...............
............OOO...............
............OO................
..............................
...................O.O........
....................OO........
...............OO...O.........
........OO......OO............
.......OO......O..............
.........O....................
..............................
..............................
.................OO...........
..........O......OOO..........
.........OOO.O...OOO..........
........OO.O.....OOO..........
........OO......O.OO..........
........OO......OOO....OO.....
........OO.OO....O.....O......
.........OO...........OO......
..........OOO.O...O.OOO.......
...............O.O............
...OO.......OO.O.O.OO.......OO
....O........O.O.O.O........O.
....OO.O.O..O.OO.OO.O..O.O.OO.
....OO.O....O.O...O.O....O.OO.
.......O..O.OO.....OO.O..O....
......OO.OOO.........OOO.OO...
........OOO...........OOO.....
.........O.............O......
</a></pre></td></tr></table></center>
<p><a name=parent>:</a><b>parent</b> A pattern is said to be a parent of the pattern it gives rise
to after one generation. Some patterns have infinitely many parents,
but others have none at all (see <a href="lex_g.htm#gardenofeden">Garden of Eden</a>). Typically
parents are considered trivial if they contain groups of cells that
can be removed without changing the result, such as isolated faraway
cells.
<p><a name=parentcells>:</a><b>parent cells</b> The three cells that cause a new cell to be born.
<p><a name=parity>:</a><b>parity</b> Even or odd, particularly as applied to the <a href="#phase">phase</a> of an
oscillator or spaceship. For example, in <a href="lex_s.htm#slowsalvo">slow salvo</a> constructions,
the <a href="lex_i.htm#intermediatetarget">intermediate targets</a> are frequently period 2, most often
because they contain <a href="lex_b.htm#blinker">blinkers</a> or <a href="lex_t.htm#trafficlight">traffic lights</a>. A glider
striking a P2 constellation will generally produce a different result
depending on its parity. Period-4 intermediate targets are rare (or
not used), so it doesn't matter for example whether an odd-parity
glider in a slow salvo is phase 1 or phase 3. Only the even/odd
parity is important.
<p><a name=partialresult>:</a><b>partial result</b> An intermediate object found by a <a href="lex_s.htm#searchprogram">search program</a>
which might be a substantial part of a complete <a href="lex_s.htm#spaceship">spaceship</a> or
<a href="lex_o.htm#oscillator">oscillator</a>, but which isn't complete.
<p>Running a partial result works for a few generations until the
<a href="lex_s.htm#speedoflight">speed of light</a> corruption from any unfinished edge destroys the
whole object. But a partial result can still be used to see whether
the object (if ever finished) would provide a desired <a href="lex_s.htm#spark">spark</a> or
<a href="#perturbation">perturbation</a>. If no partial results are found then it is likely
that no such object exists under the constraints of the search.
<p>Very large partial results can indicate that there is a good chance
that the object being searched for might actually exist (but this is
no guarantee). Rerunning the search using the partial result as a
base and relaxing some constraints, widening or adjusting the search
area, or splitting the object into multiple <a href="lex_a.htm#arm">arms</a> might result in
finding a complete working object.
<p>As an example, here is a large partial result for a period 6
<a href="lex_k.htm#knightship">knightship</a> found by Josh Ball in April 2017. The first 22 columns
were rediscovered in 2018 as part of the successful search for
<a href="lex_s.htm#sirrobin">Sir Robin</a>. See also <a href="lex_a.htm#almostknightship">almost knightship</a> for an earlier small
example by Eugene Langvagen.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....OOO...................$...O..OO..................$...O....O.................$..........................$...OOO...OO.OOO...........$.OO.O.O....O.OO...........$...O..O....O..OO..........$O..O........O.............$O....O..OO..O..O..........$.O.OOO..OO...OO...........$...OO.O.OO.O...O..........$.........OO.OOO...........$.........O.....O..........$............OOO..OOO......$...............O.OO.......$..........OO.O...OOO......$..........OO..O..OO.......$............OOOO...O......$.............OO.O..O......$...........OO.O.O.O.......$..............O...........$...........O.......OO.....$............OO.....OO.....$..............OO.O........$................OOO..O.O..$................OO...O....$.................O........$..................OOOOO.O.$...................OO..OOO$...................OO....O$.......................OO.$"
>....OOO...................
...O..OO..................
...O....O.................
..........................
...OOO...OO.OOO...........
.OO.O.O....O.OO...........
...O..O....O..OO..........
O..O........O.............
O....O..OO..O..O..........
.O.OOO..OO...OO...........
...OO.O.OO.O...O..........
.........OO.OOO...........
.........O.....O..........
............OOO..OOO......
...............O.OO.......
..........OO.O...OOO......
..........OO..O..OO.......
............OOOO...O......
.............OO.O..O......
...........OO.O.O.O.......
..............O...........
...........O.......OO.....
............OO.....OO.....
..............OO.O........
................OOO..O.O..
................OO...O....
.................O........
..................OOOOO.O.
...................OO..OOO
...................OO....O
.......................OO.
</a></pre></td></tr></table></center>
<p><a name=pd>:</a><b>PD</b> = <a href="#pentadecathlon">pentadecathlon</a>
<p><a name=pdhassler>:</a><b>PD hassler</b> = <a href="#p29pentadecathlonhassler">p29 pentadecathlon hassler</a>
<p><a name=pdpairreflector>:</a><b>PD-pair reflector</b> A pair of <a href="#pentadecathlon">pentadecathlons</a> arranged so that their
<a href="lex_v.htm#vspark">V sparks</a> turn a glider by 90 degrees. The minimum <a href="lex_r.htm#repeattime">repeat time</a> is
45 ticks.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..............OOO......$.......................$.............O...O.....$.............O...O.....$.......................$..............OOO......$.......................$.......................$..............OOO......$.......................$.............O...O.....$.............O...O.....$....................O..$..............OOO...O.O$....................OO.$.......................$O..O.OO.O..O...........$OOOO.OO.OOOO...........$O..O.OO.O..O...........$"
>..............OOO......
.......................
.............O...O.....
.............O...O.....
.......................
..............OOO......
.......................
.......................
..............OOO......
.......................
.............O...O.....
.............O...O.....
....................O..
..............OOO...O.O
....................OO.
.......................
O..O.OO.O..O...........
OOOO.OO.OOOO...........
O..O.OO.O..O...........
</a></pre></td></tr></table></center>
This was found by Mark Niemiec on 6 January 1996, which is relatively
recent considering how old <a href="#pentadecathlon">pentadecathlon</a> <a href="lex_t.htm#technology">technology</a> is.
<p><a name=pedestle>:</a><b>pedestle</b> (p5) An <a href="lex_o.htm#oscillator">oscillator</a> found by Dave Buckingham in 1973.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....O.....$....O.O....$.O..OO.....$.OOO.......$.....OOO...$...OO...O..$..O....O..O$.O.O.O.O.OO$.O.O...O.O.$OO.O.O.O.O.$O..O....O..$..O...OO...$...OOO.....$.......OOO.$.....OO..O.$....O.O....$.....O.....$"
>.....O.....
....O.O....
.O..OO.....
.OOO.......
.....OOO...
...OO...O..
..O....O..O
.O.O.O.O.OO
.O.O...O.O.
OO.O.O.O.O.
O..O....O..
..O...OO...
...OOO.....
.......OOO.
.....OO..O.
....O.O....
.....O.....
</a></pre></td></tr></table></center>
<p><a name=pennylane>:</a><b>penny lane</b> (p4) Found by Dave Buckingham, 1972.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...OO.....OO...$...O.......O...$OO.O.......O.OO$OO.O.OOOOO.O.OO$....O..O..O....$.....OOOOO.....$...............$.......O.......$......O.O......$.......O.......$"
>...OO.....OO...
...O.......O...
OO.O.......O.OO
OO.O.OOOOO.O.OO
....O..O..O....
.....OOOOO.....
...............
.......O.......
......O.O......
.......O.......
</a></pre></td></tr></table></center>
<p><a name=pentadecathlon>:</a><b>pentadecathlon</b> (p15) Found in 1970 by Conway while tracking the
history of short rows of cells, 10 cells giving this object, which is
the most <a href="lex_n.htm#natural">natural</a> <a href="lex_o.htm#oscillator">oscillator</a> of period greater than 3. In fact it
is the fifth most common <a href="lex_o.htm#oscillator">oscillator</a> overall, appearing in random
soups slightly more frequently than the <a href="lex_c.htm#clock">clock</a>, but much less
frequently than the <a href="lex_b.htm#blinker">blinker</a>, <a href="lex_t.htm#toad">toad</a>, <a href="lex_b.htm#beacon">beacon</a> or <a href="#pulsar">pulsar</a>. The
pentadecathlon can be constructed using just three gliders, as shown
in <a href="lex_g.htm#glidersynthesis">glider synthesis</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..O....O..$OO.OOOO.OO$..O....O..$"
>..O....O..
OO.OOOO.OO
..O....O..
</a></pre></td></tr></table></center>
<p>The pentadecathlon is the only known oscillator that has two
<a href="#phase">phases</a> that are different <a href="#polyomino">polyominoes</a>. It produces accessible
<a href="lex_v.htm#vspark">V sparks</a> and <a href="lex_d.htm#domino">domino</a> sparks, which give it a great capacity for
doing <a href="#perturbation">perturbations</a>, especially for period 30 based <a href="lex_t.htm#technology">technology</a>.
See <a href="lex_r.htm#relay">relay</a> for example.
<p><a name=pentant>:</a><b>pentant</b> (p5) Found by Dave Buckingham, July 1976.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OO........$.O........$.O.O......$..OO....OO$.........O$.....OOOO.$.....O....$..O...OOO.$..OOOO..O.$.....O....$....O.....$....OO....$"
>OO........
.O........
.O.O......
..OO....OO
.........O
.....OOOO.
.....O....
..O...OOO.
..OOOO..O.
.....O....
....O.....
....OO....
</a></pre></td></tr></table></center>
<p><a name=pentaplet>:</a><b>pentaplet</b> Any 5-cell <a href="#polyplet">polyplet</a>.
<p><a name=pentapole>:</a><b>pentapole</b> (p2) The <a href="lex_b.htm#barberpole">barberpole</a> of length 5.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OO......$O.O.....$........$..O.O...$........$....O.O.$.......O$......OO$"
>OO......
O.O.....
........
..O.O...
........
....O.O.
.......O
......OO
</a></pre></td></tr></table></center>
<p><a name=pentoad>:</a><b>pentoad</b> (p5) Found by Bill Gosper, June 1977. This is <a href="lex_e.htm#extensible">extensible</a>:
if an eater is moved back four spaces then another <a href="lex_z.htm#zhexomino">Z-hexomino</a> can
be inserted. (This extensibility was discovered by Scott Kim.)
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...........OO$...........O.$.........O.O.$.........OO..$.....OO......$......O......$......O......$......OO.....$..OO.........$.O.O.........$.O...........$OO...........$"
>...........OO
...........O.
.........O.O.
.........OO..
.....OO......
......O......
......O......
......OO.....
..OO.........
.O.O.........
.O...........
OO...........
</a></pre></td></tr></table></center>
<p><a name=pentomino>:</a><b>pentomino</b> Any 5-cell <a href="#polyomino">polyomino</a>. There are 12 such patterns, and
Conway assigned them all letters in the range O to Z, loosely based
on their shapes. Only in the case of the <a href="lex_r.htm#rpentomino">R-pentomino</a> has Conway's
label remained in common use, but all of them can nonetheless be
found in this lexicon.
<p><a name=period>:</a><b>period</b> The smallest number of generations it takes for an
<a href="lex_o.htm#oscillator">oscillator</a> or <a href="lex_s.htm#spaceship">spaceship</a> to reappear in its original form. The
term can also be used for a <a href="#puffer">puffer</a>, <a href="lex_w.htm#wick">wick</a>, <a href="lex_f.htm#fuse">fuse</a>, <a href="lex_s.htm#superstring">superstring</a>,
stream of <a href="lex_s.htm#spaceship">spaceships</a>, <a href="lex_f.htm#factory">factory</a> or <a href="lex_g.htm#gun">gun</a>. In the last case there
is a distinction between <a href="lex_t.htm#true">true</a> period and <a href="#pseudo">pseudo</a> period. There is
also a somewhat different concept of period for <a href="lex_w.htm#wicktrailer">wicktrailers</a>.
<p><a name=perioddoubler>:</a><b>period doubler</b> See <a href="#periodmultiplier">period multiplier</a>.
<p><a name=periodic>:</a><b>periodic</b> For <a href="lex_c.htm#circuit">circuit</a> mechanisms, "periodic" is the opposite of <a href="#p1">p1</a>
or <a href="lex_s.htm#stable">stable</a>. Periodic <a href="lex_c.htm#circuit">circuits</a> necessarily contain <a href="lex_o.htm#oscillator">oscillators</a>,
and therefore they can generally only accept input <a href="lex_s.htm#signal">signals</a> that are
<a href="lex_s.htm#synchronized">synchronized</a> to the combined <a href="#period">period</a> of those oscillators (but see
<a href="lex_u.htm#universalregulator">universal regulator</a>).
<p>For <a href="lex_s.htm#signal">signal</a> <a href="lex_s.htm#stream">streams</a>, "periodic" means that signals will only be
present in the stream at one out of every <i>n</i> ticks, where <i>n</i> is the
<a href="#period">period</a> of the stream. In a periodic <a href="lex_i.htm#intermittentstream">intermittent stream</a> there
may be gaps, so that signals do not always appear at every nth tick.
However, if a signal does appear, its distance measured in ticks from
previous and future signals will always be an exact multiple of <i>n</i>.
<p><a name=periodmultiplier>:</a><b>period multiplier</b> A term commonly used for a <a href="#pulsedivider">pulse divider</a>, because
dividing the number of <a href="lex_s.htm#signal">signals</a> in a regular stream by <i>N</i> necessarily
multiplies the <a href="#period">period</a> by <i>N</i>. The term "period multiplier" can be
somewhat misleading in this context, because most such circuits can
accept input streams that are not strictly <a href="#periodic">periodic</a>.
<p>Reactions have also been found to period double or period triple
the output of some <a href="lex_r.htm#rake">rakes</a> to create high-period rakes in a
relatively small space (i.e., an exponential increase in period for a
linear increase in size).
<p>For <a href="lex_h.htm#herschel">Herschel</a> signals and <a href="lex_g.htm#glidergun">glider guns</a>, a number of small period
doubler, tripler, and quadrupler mechanisms are known. For example,
the following <a href="lex_c.htm#conduit">conduit</a> produces one output glider after accepting
four input <a href="lex_b.htm#bheptomino">B-heptominoes</a>, or four Herschels if a conduit such as
<a href="lex_f.htm#f117">F117</a> is prepended that includes the same <a href="lex_b.htm#bfx59h">BFx59H</a> converter.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....................O........................$....................OOO......................$.......................O.....................$............OO........OO.....................$.............O...............................$.............O.O.............................$OO............OO.............................$O.O..........................................$..O..........................................$..OO.........................................$.............................................$.............................................$...........................................OO$...........................................OO$.............................................$.O...OO......................................$.OO..OO......................................$..OO.........................................$.OO..........................................$.............................................$.............................................$.............................................$.............................................$.............................................$.............................................$.............................................$.............................................$.................................OO..........$.........OO......................OO..........$........O.O..................................$........O....................................$.......OO....................................$"
>....................O........................
....................OOO......................
.......................O.....................
............OO........OO.....................
.............O...............................
.............O.O.............................
OO............OO.............................
O.O..........................................
..O..........................................
..OO.........................................
.............................................
.............................................
...........................................OO
...........................................OO
.............................................
.O...OO......................................
.OO..OO......................................
..OO.........................................
.OO..........................................
.............................................
.............................................
.............................................
.............................................
.............................................
.............................................
.............................................
.............................................
.................................OO..........
.........OO......................OO..........
........O.O..................................
........O....................................
.......OO....................................
</a></pre></td></tr></table></center>
<p>See <a href="lex_s.htm#semisnark">semi-Snark</a> and <a href="lex_t.htm#tremisnark">tremi-Snark</a> for additional examples using
<a href="lex_g.htm#glider">glider</a> streams. As of June 2018 no stable period-multiplying
<a href="lex_e.htm#elementaryconduit">elementary conduits</a> are known for a multiplication factor of five
or higher, though it is easy to construct composite ones.
<p><a name=permanentswitch>:</a><b>permanent switch</b> A <a href="lex_s.htm#signal">signal</a>-carrying <a href="lex_c.htm#circuit">circuit</a> that can be modified
so that it cleanly absorbs any future signals instead of allowing
them to pass. Optionally there may be a separate mechanism to
restore the circuit to its original function.
<p>In the following example, a glider from the northeast (shown) will
perform a simple <a href="lex_b.htm#blockpull">block pull</a> that switches off an <a href="lex_f.htm#f166">F166</a> conduit, so
that any future Herschel inputs will be cleanly absorbed. A glider
from the southwest (also shown) can restore the block to its original
position.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OO........................................................$..O........................................................$.O.........................................................$.OO...............................................OO.......$...................................................O.......$..................................................O........$..................................................OO.......$..................................O........................$..................................O.O......................$O...OO............................OO.......................$OO..OO.....................................................$.OO......................OO................................$OO.......................OO..........................OO....$.....................................................OO....$...........................................................$...........................................................$...........................................................$...........................................................$.............OO............................................$............O.O........OO..................................$..............O.......O.O..................................$......................O....................................$.....................OO.........................OO.........$................................................OO.........$...........................................................$...........................................................$..................................OO.....................OO$...................................O......................O$................................OOO....................OOO.$................................O......................O...$............................................OO.............$............................................O..............$.............................................OOO...........$...............................................O...........$"
>.OO........................................................
..O........................................................
.O.........................................................
.OO...............................................OO.......
...................................................O.......
..................................................O........
..................................................OO.......
..................................O........................
..................................O.O......................
O...OO............................OO.......................
OO..OO.....................................................
.OO......................OO................................
OO.......................OO..........................OO....
.....................................................OO....
...........................................................
...........................................................
...........................................................
...........................................................
.............OO............................................
............O.O........OO..................................
..............O.......O.O..................................
......................O....................................
.....................OO.........................OO.........
................................................OO.........
...........................................................
...........................................................
..................................OO.....................OO
...................................O......................O
................................OOO....................OOO.
................................O......................O...
............................................OO.............
............................................O..............
.............................................OOO...........
...............................................O...........
</a></pre></td></tr></table></center>
<p><a name=perpendiculargreyship>:</a><b>perpendicular grey ship</b> = <a href="lex_a.htm#againstthegraingreyship">against-the-grain grey ship</a>
<p><a name=perturb>:</a><b>perturb</b> To change the fate of an object by reacting it with other
objects. Typically, the other objects are sparks from <a href="lex_s.htm#spaceship">spaceships</a>
or <a href="lex_o.htm#oscillator">oscillators</a>, or are <a href="lex_e.htm#eater">eaters</a> or impacting spaceships.
Perturbations are typically done to turn a <a href="lex_d.htm#dirty">dirty</a> reaction into a
<a href="lex_c.htm#clean">clean</a> one, or to change the products of a reaction. In many
desirable cases the perturbing objects are not destroyed by the
reaction, or else are easily replenished.
<p><a name=perturbation>:</a><b>perturbation</b> = <a href="#perturb">perturb</a>.
<p><a name=pf35w>:</a><b>PF35W</b> One of the three <a href="lex_e.htm#elementary">elementary</a> conduits used in the composite
<a href="lex_f.htm#fx176">Fx176</a> <a href="lex_h.htm#herschelconduit">Herschel conduit</a>. It converts an input <a href="#piheptomino">pi-heptomino</a> into
an output <a href="lex_w.htm#wing">wing</a> in 35 ticks. In November 2017, Aidan F. Pierce
discovered the compact PF35W variant below, which improved the repeat
time of the Fx176 to 73 ticks and allowed <a href="lex_g.htm#glider">gliders</a> from following
<a href="lex_d.htm#dependentconduit">dependent conduits</a> to escape freely:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:O.........OO...$OOO....OO..O...$...O..O..OO....$..OO...OO..OOO.$.........O.O..O$.........O...OO$..........O....$.........OO....$...............$...............$...............$...............$...OOO.........$.....O.........$...OOO.........$...............$...............$...............$...............$...............$...............$...............$...............$..OO...........$...O...........$OOO............$O..............$"
>O.........OO...
OOO....OO..O...
...O..O..OO....
..OO...OO..OOO.
.........O.O..O
.........O...OO
..........O....
.........OO....
...............
...............
...............
...............
...OOO.........
.....O.........
...OOO.........
...............
...............
...............
...............
...............
...............
...............
...............
..OO...........
...O...........
OOO............
O..............
</a></pre></td></tr></table></center>
Several variants of the key catalyst are known, including <a href="lex_w.htm#weld">welded</a>
additions for the Fx176 that absorb the following Herschel's first
natural glider, since a standard fishhook eater doesn't quite fit.
The following is a complete <a href="lex_f.htm#fx176">Fx176</a> conduit incorporating the new
PF45W:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:   ......................O...........................$......................OOO...OO....................$..............OO.........O..O..OO.................$..............OO........OO...OO..O................$...............................O.OOO..............$...............................O....O.OO..........$................................O.O.O.O.O.........$...............................OO.OO...O..........$OO................................................$.O...................................OOOOO........$.O.O.................................O...O........$..OO...................................O..........$.........................OOO..........OOO.........$...........................O.............O........$.........................OOO............OO........$..................................................$..................................................$..................................................$..O...............................................$..O.O...............................OO...........O$..OOO...............................OO.........OOO$....O..........................................O..$...............................................O..$..............OO........OO........................$..............OO..OO.....O........................$..................O.O.OOO.........................$....................O.O...........................$....................OO....OO......................$.........................O.O....OO................$.........................O......OO................$........................OO........................$"
>   ......................O...........................
......................OOO...OO....................
..............OO.........O..O..OO.................
..............OO........OO...OO..O................
...............................O.OOO..............
...............................O....O.OO..........
................................O.O.O.O.O.........
...............................OO.OO...O..........
OO................................................
.O...................................OOOOO........
.O.O.................................O...O........
..OO...................................O..........
.........................OOO..........OOO.........
...........................O.............O........
.........................OOO............OO........
..................................................
..................................................
..................................................
..O...............................................
..O.O...............................OO...........O
..OOO...............................OO.........OOO
....O..........................................O..
...............................................O..
..............OO........OO........................
..............OO..OO.....O........................
..................O.O.OOO.........................
....................O.O...........................
....................OO....OO......................
.........................O.O....OO................
.........................O......OO................
........................OO........................
</a></pre></td></tr></table></center>
<p><a name=phase>:</a><b>phase</b> A representative generation of a periodic object such as an
<a href="lex_o.htm#oscillator">oscillator</a> or <a href="lex_s.htm#spaceship">spaceship</a>. The number of phases is equal to the
<a href="#period">period</a> of the object. The phases of an object usually repeat in
the same cyclic sequence forever, although some <a href="#perturbation">perturbations</a> can
cause a <a href="#phasechange">phase change</a>.
<p><a name=phasechange>:</a><b>phase change</b> A <a href="#perturbation">perturbation</a> of a periodic object that causes the
object to skip forward or backward by one or more <a href="#phase">phases</a>. If the
perturbation is repeated indefinitely, this can effectively change
the <a href="#period">period</a> of the object. An example of this, found by Dean
Hickerson in November 1998, is shown below. In this example, the
period of the <a href="lex_o.htm#oscillator">oscillator</a> would be 7 if the <a href="lex_m.htm#mold">mold</a> were removed, but
the period is increased to 8 because of the repeated phase changes
caused by the mold's <a href="lex_s.htm#spark">spark</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..........O....$.........O.OO..$..OO.........O.$..O......O..O.O$.......O...O..O$OOOOOO.O....OO.$O..............$.OO.OO...OO....$..O.O....O.O...$..O.O......O...$...O.......OO..$"
>..........O....
.........O.OO..
..OO.........O.
..O......O..O.O
.......O...O..O
OOOOOO.O....OO.
O..............
.OO.OO...OO....
..O.O....O.O...
..O.O......O...
...O.......OO..
</a></pre></td></tr></table></center>
<p>The following pattern demonstrates a p4 <i>c</i>/2 <a href="lex_s.htm#spaceship">spaceship</a> found by
Jason Summers, in which the phase is changed as it deletes a
<a href="lex_f.htm#forwardglider">forward glider</a>. This phase change allows the spaceship to be used
to delete a glider wave produced by a <a href="lex_r.htm#rake">rake</a> whose period is 2 (mod
4).
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:........O...........................$.......OOO.OO.......................$......OO...O.OO.....................$.....OO..O.....O....................$......O.....O...O.OOO...............$.....OO.....O...O.O..O..............$...OO.O.OO....O.O.O...O.............$....O.O..OO...........O.............$.OO.O..O..O.........O...............$.OO.O.....OO.........O.OOO..........$.O.O.............OOO.O.O.OO.........$OO.OO...........OO.O..O.O.O.........$..............OO.O...OOO..OO.....OO.$.............O...O......O........O.O$............O.....O..OO.O.OO.....O..$...........O..O.O......O.O..........$...........O.....OO....OOO..........$.............O..........O...........$..........O.O...........O...........$.........OO.O.OOO...................$........O.O.O...O...................$.......OO.O.........................$......O...O.....OO..................$....................................$......OO.OO.........................$"
>........O...........................
.......OOO.OO.......................
......OO...O.OO.....................
.....OO..O.....O....................
......O.....O...O.OOO...............
.....OO.....O...O.O..O..............
...OO.O.OO....O.O.O...O.............
....O.O..OO...........O.............
.OO.O..O..O.........O...............
.OO.O.....OO.........O.OOO..........
.O.O.............OOO.O.O.OO.........
OO.OO...........OO.O..O.O.O.........
..............OO.O...OOO..OO.....OO.
.............O...O......O........O.O
............O.....O..OO.O.OO.....O..
...........O..O.O......O.O..........
...........O.....OO....OOO..........
.............O..........O...........
..........O.O...........O...........
.........OO.O.OOO...................
........O.O.O...O...................
.......OO.O.........................
......O...O.....OO..................
....................................
......OO.OO.........................
</a></pre></td></tr></table></center>
<p>Phase changing reactions have enabled the construction of
spaceships having periods that were otherwise unknown, and also allow
the construction of period-doubling and period-tripling <a href="lex_c.htm#convoy">convoys</a> to
easily produce very high period rakes.
<p>See also <a href="lex_b.htm#blinkerpuffer">blinker puffer</a>.
<p><a name=phaseshift>:</a><b>phase shift</b> = <a href="#phasechange">phase change</a>
<p><a name=phi>:</a><b>phi</b> The following common <a href="lex_s.htm#spark">spark</a>. The name comes from the shape in
the generation after the one shown here.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OOO.$O...O$O...O$.OOO.$"
>.OOO.
O...O
O...O
.OOO.
</a></pre></td></tr></table></center>
One <a href="lex_o.htm#oscillator">oscillator</a> which produces this spark is <a href="lex_t.htm#tannersp46">Tanner's p46</a>. The
<a href="#pentadecathlon">pentadecathlon</a> produces a slightly corrupted version of this spark.
<p><a name=phicalculator>:</a><b>phi calculator</b> (p1 circuitry) See <a href="#picalculator">pi calculator</a>.
<p><a name=phoenix>:</a><b>phoenix</b> Any pattern all of whose cells die in every generation, but
which never dies as a whole. A <a href="lex_s.htm#spaceship">spaceship</a> cannot be a phoenix, and
in fact every finite phoenix eventually evolves into an <a href="lex_o.htm#oscillator">oscillator</a>.
The following 12-cell oscillator (found by the MIT group in December
1971) is the smallest known phoenix, and is sometimes called simply
"the phoenix".
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....O...$..O.O...$......O.$OO......$......OO$.O......$...O.O..$...O....$"
>....O...
..O.O...
......O.
OO......
......OO
.O......
...O.O..
...O....
</a></pre></td></tr></table></center>
This is <a href="lex_e.htm#extensible">extensible</a> and is just the first of a family of phoenixes
made by joining <a href="lex_c.htm#component">components</a> together to form a loop. Here is
another member of this family.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....................O.......O......$.....................O.O.....O.O....$.................O.O.....O.O........$.................O.......O......OO..$.....O.......O.O....................$.....O.O.....O...................O..$...O.....O.O........................$.........O........................OO$..OO................................$..................................O.$.O..................................$................................OO..$OO........................O.........$........................O.O.....O...$..O...................O.....O.O.....$....................O.O.......O.....$..OO......O.......O.................$........O.O.....O.O.................$....O.O.....O.O.....................$......O.......O.....................$"
>.....................O.......O......
.....................O.O.....O.O....
.................O.O.....O.O........
.................O.......O......OO..
.....O.......O.O....................
.....O.O.....O...................O..
...O.....O.O........................
.........O........................OO
..OO................................
..................................O.
.O..................................
................................OO..
OO........................O.........
........................O.O.....O...
..O...................O.....O.O.....
....................O.O.......O.....
..OO......O.......O.................
........O.O.....O.O.................
....O.O.....O.O.....................
......O.......O.....................
</a></pre></td></tr></table></center>
Every known phoenix oscillator has period 2. In January 2000,
Stephen Silver showed that a period 3 oscillator cannot be a phoenix.
The situation for higher periods is unknown.
<p>An easy <a href="lex_s.htm#synthesis">synthesis</a> of the phoenix is possible using four blocks as
<a href="lex_s.htm#seed">seeds</a>. A <a href="#puffer">puffer</a> creating a growing row of phoenixes has the
unusual property that the percentage of live cells that stay alive
for more than one generation approaches zero. See <a href="lex_l.htm#lonedotagar">lone dot agar</a>
for an example of an infinite phoenix.
<p><a name=pi>:</a><b>pi</b> = <a href="#piheptomino">pi-heptomino</a>
<p><a name=pianolabreeder>:</a><b>Pianola breeder</b> A series of patterns by Paul Tooke in 2010, based on
a simplification and extension of the <a href="lex_g.htm#gemini">Gemini</a> spaceship's
construction mechanism. Tooke produced a number of
slow-salvo-constructed patterns with <a href="lex_s.htm#superlineargrowth">superlinear growth</a>, including
a series of breeder patterns of previously unknown types. For some
patterns, the Gemini's two <a href="lex_c.htm#constructionarm">construction arms</a> were moved to a
permanent stationary platform, using fourteen glider-loop channels
instead of twelve.
<p>Some of these breeder patterns remain difficult to classify
unambiguously. For example, one pattern was designed to be an MSS
breeder - a modified <a href="lex_g.htm#gemini">Gemini</a> spaceship puffing <a href="lex_s.htm#slidegun">slide guns</a> which
build lines of <a href="lex_b.htm#block">blocks</a>. However, the slide guns produce both moving
and stationary objects at a linear rate, because streams of gliders
are needed to reach out to the construction zone to do the <a href="#push">push</a>
reaction and build more blocks. The pattern could therefore be
classified as a hybrid MSM/MSS breeder. Other breeder patterns
utilizing slide guns and <a href="lex_u.htm#universalconstructor">universal constructor</a> technology are
likely to cause similar classification ambiguities.
<p><a name=picalculator>:</a><b>pi calculator</b> (p1 circuitry) A device constructed by Adam P. Goucher
in February 2010, which calculates the decimal digits of pi (the
transcendental number, not the Life pattern!) and displays them in
the Life universe as 8x10 dot matrix characters formed by
arrangements of blocks along a diagonal stripe at the top. A <a href="#push">push</a>
reaction moves a ten-block diagonal cursor to the next position as
part of the "printing" operation for each new digit.
<p>The actual calculation is done in binary, using a streaming spigot
algorithm based on linear fractional transformations. The pi
calculator is made up of a 188-state computer connected to a printing
device via period-8 <a href="lex_r.htm#regulator">regulators</a> and a binary-to-decimal conversion
mechanism. The complete pattern can be found in <a href="lex_g.htm#golly">Golly</a>'s Very Large
Patterns online archive, along with the very similar 177-state phi
calculator which uses a simpler algorithm to calculate and print the
Golden Ratio.
<p><a name=piclimber>:</a><b>pi climber</b> The reaction that defines rate of travel of the
<a href="lex_c.htm#caterpillar">Caterpillar</a> spaceship. A pi climber consists of a pi-heptomino
"climbing" a chain of blinkers, moving 17 cells every 45 ticks, and
leaving behind an identical chain of blinkers, shifted downward by 6
cells. A single pi climber does not produce any gliders or other
output, but two or more of them travelling on nearby blinker chains
can be arranged to emit gliders every 45 ticks. Compare
<a href="lex_h.htm#herschelpairclimber">Herschel-pair climber</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..O..$..O..$..O..$.....$.....$.....$.....$.....$.....$.....$.....$.....$.....$.....$.....$..O..$.OOO.$.O.O.$"
>..O..
..O..
..O..
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
..O..
.OOO.
.O.O.
</a></pre></td></tr></table></center>
<p><a name=piheptomino>:</a><b>pi-heptomino</b> (stabilizes at time 173) A common pattern. The name is
also applied to later generations of this object. In a <a href="#piship">pi ship</a>,
for example, the pi-heptomino itself never arises.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OOO$O.O$O.O$"
>OOO
O.O
O.O
</a></pre></td></tr></table></center>
<p><a name=pincers>:</a><b>pincers</b> = <a href="lex_g.htm#greatonoff">great on-off</a>
<p><a name=pinwheel>:</a><b>pinwheel</b> (p4) Found by Simon Norton, April 1970. Compare <a href="lex_c.htm#clockii">clock II</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:......OO....$......OO....$............$....OOOO....$OO.O....O...$OO.O..O.O...$...O...OO.OO$...O.O..O.OO$....OOOO....$............$....OO......$....OO......$"
>......OO....
......OO....
............
....OOOO....
OO.O....O...
OO.O..O.O...
...O...OO.OO
...O.O..O.OO
....OOOO....
............
....OO......
....OO......
</a></pre></td></tr></table></center>
<p><a name=piorbital>:</a><b>pi orbital</b> (p168) Found by Noam Elkies, August 1995. In this
<a href="lex_o.htm#oscillator">oscillator</a>, a <a href="#piheptomino">pi-heptomino</a> is turned ninety degrees every 42
generations. A second pi can be inserted to reduce the period to 84.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..............OO....OO....OO...............................$.............O..O.O....O.O..O..............................$.............OOO..........OOO..............................$................OO......OO.................................$...............O..OOOOOO..O................................$...............OO........OO................................$...........................................................$........O.............................OO..........O........$.......O...OOO......O.........O.......OO.........O.O.......$........O.OOOOO..........OOO...O...........................$............O...O.....O.OOOOO.O..................O.........$............OO....OOO.....O......................OO........$............OO....OOO....OO...................OOOOO........$...................O.....OO...................OO.OO.....OO.$.................................................O......O.O$.....................................................OO.O.O$.....................................................O.O.O.$.......................................................O...$...................................OOO.........O.O...O..O..$.......OO..........................O..O........O..O.....O..$.......OO..............................O.......O.O..O...O..$...................................O..O.............O...O..$...................................OOO..................O..$.....................................................O..O..$................................................O......O...$.............................................OO.OO...O.O.O.$.............................................OOOOO...OO.O.O$.........O......................................OO......O.O$........O.O.....................................O.......OO.$...........................................................$.OO.......O.....................................O.O........$O.O......OO......................................O.........$O.O.OO...OOOOO.............................................$.O.O.O...OO.OO.............................................$...O......O................................................$..O..O.....................................................$..O........................................................$..O...O....................................................$..O...O..O.O......................................OO.......$..O.....O..O......................................OO.......$..O..O...O.O...............................................$...O.......................................................$.O.O.O.....................................................$O.O.OO.....................................................$O.O......O.................................................$.OO.....OO.OO...................OO.....O...................$........OOOOO...................OO....OOO....OO............$........OO......................O.....OOO....OO............$.........O..................O.OOOOO.O.....O...O............$...........................O...OOO..........OOOOO.O........$.......O.O.........OO.......O.........O......OOO...O.......$........O..........OO.............................O........$...........................................................$................................OO........OO...............$................................O..OOOOOO..O...............$.................................OO......OO................$..............................OOO..........OOO.............$..............................O..O.O....O.O..O.............$...............................OO....OO....OO..............$"
>..............OO....OO....OO...............................
.............O..O.O....O.O..O..............................
.............OOO..........OOO..............................
................OO......OO.................................
...............O..OOOOOO..O................................
...............OO........OO................................
...........................................................
........O.............................OO..........O........
.......O...OOO......O.........O.......OO.........O.O.......
........O.OOOOO..........OOO...O...........................
............O...O.....O.OOOOO.O..................O.........
............OO....OOO.....O......................OO........
............OO....OOO....OO...................OOOOO........
...................O.....OO...................OO.OO.....OO.
.................................................O......O.O
.....................................................OO.O.O
.....................................................O.O.O.
.......................................................O...
...................................OOO.........O.O...O..O..
.......OO..........................O..O........O..O.....O..
.......OO..............................O.......O.O..O...O..
...................................O..O.............O...O..
...................................OOO..................O..
.....................................................O..O..
................................................O......O...
.............................................OO.OO...O.O.O.
.............................................OOOOO...OO.O.O
.........O......................................OO......O.O
........O.O.....................................O.......OO.
...........................................................
.OO.......O.....................................O.O........
O.O......OO......................................O.........
O.O.OO...OOOOO.............................................
.O.O.O...OO.OO.............................................
...O......O................................................
..O..O.....................................................
..O........................................................
..O...O....................................................
..O...O..O.O......................................OO.......
..O.....O..O......................................OO.......
..O..O...O.O...............................................
...O.......................................................
.O.O.O.....................................................
O.O.OO.....................................................
O.O......O.................................................
.OO.....OO.OO...................OO.....O...................
........OOOOO...................OO....OOO....OO............
........OO......................O.....OOO....OO............
.........O..................O.OOOOO.O.....O...O............
...........................O...OOO..........OOOOO.O........
.......O.O.........OO.......O.........O......OOO...O.......
........O..........OO.............................O........
...........................................................
................................OO........OO...............
................................O..OOOOOO..O...............
.................................OO......OO................
..............................OOO..........OOO.............
..............................O..O.O....O.O..O.............
...............................OO....OO....OO..............
</a></pre></td></tr></table></center>
<p><a name=piportraitor>:</a><b>pi portraitor</b> (p32) Found by Robert Wainwright in 1984 or 1985.
Compare with <a href="lex_g.htm#gourmet">gourmet</a> and <a href="#popover">popover</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...........OO...........$......OO.O....O.OO......$......O..........O......$.......OO......OO.......$....OOO..OOOOOO..OOO....$....O..O........O..O....$.OO.O.O..........O.O.OO.$.O.O.O............O.O.O.$...O................O...$.O..O..............O..O.$....O.......OOO....O....$O...O.......O.O....O...O$O...O.......O.O....O...O$....O..............O....$.O..O..............O..O.$...O................O...$.O.O.O............O.O.O.$.OO.O.O..........O.O.OO.$....O..O........O..O....$....OOO..OOOOOO..OOO....$.......OO......OO.......$......O..........O......$......OO.O....O.OO......$...........OO...........$"
>...........OO...........
......OO.O....O.OO......
......O..........O......
.......OO......OO.......
....OOO..OOOOOO..OOO....
....O..O........O..O....
.OO.O.O..........O.O.OO.
.O.O.O............O.O.O.
...O................O...
.O..O..............O..O.
....O.......OOO....O....
O...O.......O.O....O...O
O...O.......O.O....O...O
....O..............O....
.O..O..............O..O.
...O................O...
.O.O.O............O.O.O.
.OO.O.O..........O.O.OO.
....O..O........O..O....
....OOO..OOOOOO..OOO....
.......OO......OO.......
......O..........O......
......OO.O....O.OO......
...........OO...........
</a></pre></td></tr></table></center>
<p><a name=pipsquirt>:</a><b>pipsquirt</b> = <a href="#pipsquirter">pipsquirter</a>
<p><a name=pipsquirter>:</a><b>pipsquirter</b> An <a href="lex_o.htm#oscillator">oscillator</a> that produces a <a href="lex_d.htm#domino">domino</a> <a href="lex_s.htm#spark">spark</a> that is
orientated parallel to the direction from which it is produced (in
contrast to domino sparkers like the <a href="#pentadecathlon">pentadecathlon</a> and <a href="lex_h.htm#hwss">HWSS</a>,
which produce domino sparks perpendicular to the direction of
production). See <a href="#p6pipsquirter">p6 pipsquirter</a>, <a href="#p7pipsquirter">p7 pipsquirter</a>.
<p><a name=piship>:</a><b>pi ship</b> A <a href="lex_g.htm#growingspaceship">growing spaceship</a> in which the back part consists of a
<a href="#piheptomino">pi-heptomino</a> travelling at a speed of 3<i>c</i>/10. The first example was
constructed by David Bell. All known pi ships are too large to show
here, but the following diagram shows how the pi fuse works.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:............O............$...........O.O...........$OO........OO.OO........OO$OO.....................OO$"
>............O............
...........O.O...........
OO........OO.OO........OO
OO.....................OO
</a></pre></td></tr></table></center>
<p><a name=piston>:</a><b>piston</b> (p2) Found in 1971.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OO.......OO$O.O..O..O.O$..OOOO..O..$O.O..O..O.O$OO.......OO$"
>OO.......OO
O.O..O..O.O
..OOOO..O..
O.O..O..O.O
OO.......OO
</a></pre></td></tr></table></center>
<p><a name=piwave>:</a><b>pi wave</b> A line of <a href="#piheptomino">pi-heptominoes</a> stabilizing one another. For
example, an infinite line of pi-heptominoes arranged as shown below
produces a pi wave that moves at a speed of 3<i>c</i>/10 with period 30, and
leaves no debris.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OOO...............OOO...............OOO...............OOO$O.O...............O.O...............O.O...............O.O$O.O...............O.O...............O.O...............O.O$"
>OOO...............OOO...............OOO...............OOO
O.O...............O.O...............O.O...............O.O
O.O...............O.O...............O.O...............O.O
</a></pre></td></tr></table></center>
<p><a name=pixel>:</a><b>pixel</b> = <a href="lex_c.htm#cell">cell</a>
<p><a name=plet>:</a><b>plet</b> = <a href="#polyplet">polyplet</a>
<p><a name=polyomino>:</a><b>polyomino</b> A finite collection of orthogonally connected cells. The
mathematical study of polyominoes was initiated by Solomon Golomb in
1953. Conway's early investigations of Life and other cellular
automata involved tracking the histories of small polyominoes, this
being a reasonable way to ascertain the typical behaviour of
different cellular automata when the patterns had to be evolved by
hand rather than by computer. Polyominoes have no special
significance in Life, but their extensive study during the early
years lead to a number of important discoveries and has influenced
the terminology of Life. (Note on spelling: As with "dominoes" the
plural may also be spelt without an e. In this lexicon I have
followed Golomb in using the longer form.)
<p>It is possible for a polyomino to be an <a href="lex_o.htm#oscillator">oscillator</a>. In fact
there are infinitely many examples of such polyominoes, namely the
<a href="lex_c.htm#cross">cross</a> and its larger analogues. The only other known examples are
the <a href="lex_b.htm#block">block</a>, the <a href="lex_b.htm#blinker">blinker</a>, the <a href="lex_t.htm#toad">toad</a>, the <a href="lex_s.htm#star">star</a> and (in two
different phases) the <a href="#pentadecathlon">pentadecathlon</a>.
<p>A polyomino can also be a <a href="lex_s.htm#spaceship">spaceship</a>, as the <a href="lex_l.htm#lwss">LWSS</a>, <a href="lex_m.htm#mwss">MWSS</a> and
<a href="lex_h.htm#hwss">HWSS</a> show.
<p><a name=polyplet>:</a><b>polyplet</b> A finite collection of orthogonally or diagonally connected
cells. This king-wise connectivity is a more natural concept in Life
than the orthogonal connectivity of the <a href="#polyomino">polyomino</a>.
<p><a name=pond>:</a><b>pond</b> (p1)
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OO.$O..O$O..O$.OO.$"
>.OO.
O..O
O..O
.OO.
</a></pre></td></tr></table></center>
<p><a name=pondonpond>:</a><b>pond on pond</b> (p1) This term is often used to mean <a href="lex_b.htm#bipond">bi-pond</a>, but may
also be used of the following <a href="#pseudostilllife">pseudo still life</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OO...OO.$O..O.O..O$O..O.O..O$.OO...OO.$"
>.OO...OO.
O..O.O..O
O..O.O..O
.OO...OO.
</a></pre></td></tr></table></center>
<p><a name=popover>:</a><b>popover</b> (p32) Found by Robert Wainwright in August 1984. Compare
with <a href="lex_g.htm#gourmet">gourmet</a> and <a href="#piportraitor">pi portraitor</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....................O..........$.....................O..........$.....................OOO........$.............OO.......OO........$.............OO..OOO..OO........$...................OOO..........$...................OOO..........$..............OO................$..OOO........O..O...............$..OOO........O.O................$OOO..OO...O...O....OOO..........$.....OO...O.....................$....OOO...O.....................$....O.................OO...OO...$....O...........OOO..O..O..OO...$........O.......O.O...O.O.......$.......O.O......O.O....O........$...OO..O..O................O....$...OO...OO.................O....$.....................O...OOO....$.....................O...OO.....$..........OOO........O...OO..OOO$.................OO........OOO..$................O..O.......OOO..$................O.O.............$..........OOO....O..............$..........OOO...................$........OO..OOO..OO.............$........OO.......OO.............$........OOO.....................$..........O.....................$..........O.....................$"
>.....................O..........
.....................O..........
.....................OOO........
.............OO.......OO........
.............OO..OOO..OO........
...................OOO..........
...................OOO..........
..............OO................
..OOO........O..O...............
..OOO........O.O................
OOO..OO...O...O....OOO..........
.....OO...O.....................
....OOO...O.....................
....O.................OO...OO...
....O...........OOO..O..O..OO...
........O.......O.O...O.O.......
.......O.O......O.O....O........
...OO..O..O................O....
...OO...OO.................O....
.....................O...OOO....
.....................O...OO.....
..........OOO........O...OO..OOO
.................OO........OOO..
................O..O.......OOO..
................O.O.............
..........OOO....O..............
..........OOO...................
........OO..OOO..OO.............
........OO.......OO.............
........OOO.....................
..........O.....................
..........O.....................
</a></pre></td></tr></table></center>
<p><a name=population>:</a><b>population</b> The number of ON cells.
<p><a name=ppentomino>:</a><b>P-pentomino</b> Conway's name for the following <a href="#pentomino">pentomino</a>, a common
<a href="lex_s.htm#spark">spark</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OO$OO$O.$"
>OO
OO
O.
</a></pre></td></tr></table></center>
<p><a name=pps>:</a><b>PPS</b> (<i>c</i>/5 orthogonally, p30) A pre-pulsar spaceship. Any of three
different p30 <i>c</i>/5 orthogonal <a href="lex_s.htm#spaceship">spaceships</a> in which a <a href="#prepulsar">pre-pulsar</a> is
pushed by a pair of <a href="lex_s.htm#spider">spiders</a>. The back sparks of the spaceship can
be used to perturb gliders in many different ways, allowing the easy
construction of <i>c</i>/5 puffers. The first PPS was found by David Bell
in May 1998 based on a p15 pre-pulsar spaceship found by Noam Elkies
in December 1997. See also <a href="lex_s.htm#spps">SPPS</a> and <a href="lex_a.htm#apps">APPS</a>.
<p>The pattern below shows the basic mechanism of a PPS. The two
isolated sparks at the left and right sides are the <a href="lex_e.htm#edgespark">edge sparks</a>
from the two supporting spiders.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...O.....O...$..O.O...O.O..$.............$..OOO...OOO..$.............$.............$.............$..OOO...OOO..$.............$O.O.O...O.O.O$...O.....O...$"
>...O.....O...
..O.O...O.O..
.............
..OOO...OOO..
.............
.............
.............
..OOO...OOO..
.............
O.O.O...O.O.O
...O.....O...
</a></pre></td></tr></table></center>
<p><a name=prebeehive>:</a><b>pre-beehive</b> The following common <a href="#parent">parent</a> of the <a href="lex_b.htm#beehive">beehive</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OOO$OOO$"
>OOO
OOO
</a></pre></td></tr></table></center>
<p><a name=preblock>:</a><b>pre-block</b> The following common <a href="#parent">parent</a> of the <a href="lex_b.htm#block">block</a>. Another such
pattern is the <a href="lex_g.htm#grin">grin</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:O.$OO$"
>O.
OO
</a></pre></td></tr></table></center>
<p><a name=precursor>:</a><b>precursor</b> = <a href="#predecessor">predecessor</a>
<p><a name=predecessor>:</a><b>predecessor</b> Any pattern that evolves into a given pattern after one
or more generations.
<p><a name=prepreblock>:</a><b>pre-pre-block</b> A common predecessor to the <a href="#preblock">pre-block</a> (and thus the
<a href="lex_b.htm#block">block</a>):
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:O.O$.OO$"
>O.O
.OO
</a></pre></td></tr></table></center>
This is easily created by a two-glider collision. Hitting the
pre-pre-block with a glider can create a <a href="lex_m.htm#mwss">MWSS</a>. Both of these
reactions are shown below:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.O..........$..O.........$OOO.........$............$............$...OOO....OO$.....O...OO.$....O......O$"
>.O..........
..O.........
OOO.........
............
............
...OOO....OO
.....O...OO.
....O......O
</a></pre></td></tr></table></center>
<p><a name=prepulsar>:</a><b>pre-pulsar</b> A common <a href="#predecessor">predecessor</a> of the <a href="#pulsar">pulsar</a>, such as that shown
below. This duplicates itself in 15 generations. (It fails,
however, to be a true <a href="lex_r.htm#replicator">replicator</a> because of the way the two copies
then interact.)
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OOO...OOO$O.O...O.O$OOO...OOO$"
>OOO...OOO
O.O...O.O
OOO...OOO
</a></pre></td></tr></table></center>
<p>A pair of <a href="lex_t.htm#tub">tubs</a> can be placed to eat half the pre-pulsar as it
replicates; this gives the p30 oscillator <a href="lex_e.htm#eureka">Eureka</a> where the
pre-pulsar's replication becomes a movement back and forth. See
<a href="lex_t.htm#twirlingttetsonsii">twirling T-tetsons II</a> for a variation on this idea. By other means
the replication of the pre-pulsar can be made to occur in just 14
generations as half of it is eaten; this allows the construction of
p28 and p29 oscillators. The pre-pulsar was also a vital component
of the first known p26 and p47 oscillators.
<p>See also <a href="#pps">PPS</a>.
<p><a name=prepulsarspaceship>:</a><b>pre-pulsar spaceship</b> = <a href="#pps">PPS</a>.
<p><a name=pressurecooker>:</a><b>pressure cooker</b> (p3) Found by the MIT group in September 1971.
Compare <a href="lex_m.htm#minipressurecooker">mini pressure cooker</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....O.....$....O.O....$....O.O....$...OO.OO...$O.O.....O.O$OO.O.O.O.OO$...O...O...$...O...O...$....OOO....$...........$...O.OO....$...OO.O....$"
>.....O.....
....O.O....
....O.O....
...OO.OO...
O.O.....O.O
OO.O.O.O.OO
...O...O...
...O...O...
....OOO....
...........
...O.OO....
...OO.O....
</a></pre></td></tr></table></center>
<p><a name=primer>:</a><b>primer</b> A pattern originally constructed by Dean Hickerson in November
1991 that emits a stream of <a href="lex_l.htm#lwss">LWSSs</a> representing the prime numbers.
Some improvements were found by Jason Summers in October 2005.
<p><a name=prng>:</a><b>PRNG</b> = <a href="#pseudorandomnumbergenerator">pseudo-random number generator</a>
<p><a name=propagator>:</a><b>propagator</b> = <a href="lex_l.htm#linearpropagator">linear propagator</a>
<p><a name=protein>:</a><b>protein</b> (p3) Found by Dave Buckingham, November 1972.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:....OO.......$....O........$......O......$..OOOO.O.OO..$.O.....O.O..O$.O..OO.O.O.OO$OO.O.....O...$...O..OO.O...$...O....O....$....OOOO.....$.............$....OO.......$....OO.......$"
>....OO.......
....O........
......O......
..OOOO.O.OO..
.O.....O.O..O
.O..OO.O.O.OO
OO.O.....O...
...O..OO.O...
...O....O....
....OOOO.....
.............
....OO.......
....OO.......
</a></pre></td></tr></table></center>
<p><a name=pseudo>:</a><b>pseudo</b> Opposite of <a href="lex_t.htm#true">true</a>. A <a href="lex_g.htm#gun">gun</a> emitting a period <i>n</i> <a href="lex_s.htm#stream">stream</a> of
spaceships (or rakes) is said to be a pseudo period <i>n</i> gun if its
mechanism oscillates with a period greater than <i>n</i>. This period will
necessarily be a multiple of <i>n</i>. If the base mechanism's period is
instead a fraction of <i>n</i>, then a <a href="#periodmultiplier">period multiplier</a> must also be
present which is considered to be part of the mechanism, and the gun
as a whole is still a true period gun. For example, a <a href="lex_f.htm#filter">filter</a> may
be used on a lower-period gun to produce a compound gun such as the
true <a href="#p48gun">p48 gun</a>.
<p>Pseudo period <i>n</i> glider guns are known to exist for all periods
greater than or equal to 14, with smaller periods being impossible.
All known <a href="#p14gun">p14 guns</a> are pseudo guns requiring several <a href="lex_s.htm#signal">signal</a>
<a href="lex_i.htm#inject">injections</a>, so they are quite large. The following smaller example
is a pseudo period 123 gun, interleaving the streams from two true
period 246 guns:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..................................O...........................$..................................OOO.........................$................................OO...O........................$...............................O.O.OO.O.......................$..............................O..O..O.O.......................$....................................O.OO......................$..................................O.O.........................$......................OOO.......O.O.O.........................$.................................OO.OO........................$.....................O..O.....................................$OO...................OOO......................................$.O............................................................$.O.O...................OO.OO..................................$..OO...............OO..OO.O.O............OO...................$...................OO..OO...O............O....................$...........................OOO.........O.O...........OO.......$.......................OO..OOO.........OO............O.O......$..................O.O..OOO............................OOO.....$..................O.O...OO.............................OO.....$...................O.................................O.O......$................................................OO..O.O.......$................................................O.O..O........$.................................................OOOO.........$.............................OO...................OO..........$.............................OO...............................$..............................................................$..............................................................$.....................................OOOO.....................$....................................OOOOO.O...................$.....................................O..O.O...................$.....O...................................OO...................$....O.OOOO.............................O.O....................$...O.O.OOO..........................OO............O.........OO$..O.O..............................O.OOOO..........O........O.$...O...............................O...OO........OOO......O.O.$...OO.............OO................OO.O..................OO..$...OO.............O.O................OOO......................$...OO..............OOO........................................$....................OO........................................$..................O.O.........................................$.............OO..O.O..........................................$.............O.O..O...........................................$..............OOOO..............................OO............$...............OO...............................OO............$....................OO.OO.....................................$.....................O.O......................................$.....................O........................................$..................OO.O..O.....................................$...................O.O.OOO....................................$...................O.OO...O...................................$....................O...OO....................................$.....................OOO......................................$.......................O......................................$"
>..................................O...........................
..................................OOO.........................
................................OO...O........................
...............................O.O.OO.O.......................
..............................O..O..O.O.......................
....................................O.OO......................
..................................O.O.........................
......................OOO.......O.O.O.........................
.................................OO.OO........................
.....................O..O.....................................
OO...................OOO......................................
.O............................................................
.O.O...................OO.OO..................................
..OO...............OO..OO.O.O............OO...................
...................OO..OO...O............O....................
...........................OOO.........O.O...........OO.......
.......................OO..OOO.........OO............O.O......
..................O.O..OOO............................OOO.....
..................O.O...OO.............................OO.....
...................O.................................O.O......
................................................OO..O.O.......
................................................O.O..O........
.................................................OOOO.........
.............................OO...................OO..........
.............................OO...............................
..............................................................
..............................................................
.....................................OOOO.....................
....................................OOOOO.O...................
.....................................O..O.O...................
.....O...................................OO...................
....O.OOOO.............................O.O....................
...O.O.OOO..........................OO............O.........OO
..O.O..............................O.OOOO..........O........O.
...O...............................O...OO........OOO......O.O.
...OO.............OO................OO.O..................OO..
...OO.............O.O................OOO......................
...OO..............OOO........................................
....................OO........................................
..................O.O.........................................
.............OO..O.O..........................................
.............O.O..O...........................................
..............OOOO..............................OO............
...............OO...............................OO............
....................OO.OO.....................................
.....................O.O......................................
.....................O........................................
..................OO.O..O.....................................
...................O.O.OOO....................................
...................O.OO...O...................................
....................O...OO....................................
.....................OOO......................................
.......................O......................................
</a></pre></td></tr></table></center>
<p>The same distinction between true and pseudo also exists for
<a href="#puffer">puffers</a>.
<p><a name=pseudobarberpole>:</a><b>pseudo-barberpole</b> (p5) Found by Achim Flammenkamp in August 1994. In
terms of its minimum <a href="#population">population</a> of 15 this is the smallest known p5
<a href="lex_o.htm#oscillator">oscillator</a>. See also <a href="lex_b.htm#barberpole">barberpole</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..........OO$...........O$.........O..$.......O.O..$............$.....O.O....$............$...O.O......$............$..OO........$O...........$OO..........$"
>..........OO
...........O
.........O..
.......O.O..
............
.....O.O....
............
...O.O......
............
..OO........
O...........
OO..........
</a></pre></td></tr></table></center>
<p><a name=pseudorandomglidergenerator>:</a><b>pseudo-random glider generator</b> A <a href="#pseudorandomnumbergenerator">pseudo-random number generator</a> in
which the bits are represented by the presence or absence of
<a href="lex_g.htm#glider">gliders</a>. The first pseudo-random glider generator was built by
Bill Gosper. David Bell built the first moving one in 1997, using
<i>c</i>/3 <a href="lex_r.htm#rake">rakes</a>.
<p><a name=pseudorandomnumbergenerator>:</a><b>pseudo-random number generator</b> A pseudo-random number generator
(PRNG) is an algorithm that produces a sequence of bits that looks
random (but cannot really be random, being algorithmically
determined).
<p>In Life, the term refers to a PRNG implemented as a Life pattern,
with the bits represented by the presence or absence of objects such
as <a href="lex_g.htm#glider">gliders</a> or <a href="lex_b.htm#block">blocks</a>. Such a PRNG usually contains gliders or
other <a href="lex_s.htm#spaceship">spaceships</a> in a loop with a feedback mechanism that causes
later spaceships to interfere with the generation of earlier
spaceships. The <a href="#period">period</a> can be very high, as a loop of <i>n</i> spaceships
has 2<sup><i>n</i></sup> possible states.
<p><a name=pseudostilllife>:</a><b>pseudo still life</b> A <a href="lex_s.htm#stable">stable</a> pattern whose live cells are either
immediately adjacent to each other, or are connected into a single
group by adjacent dead cells where birth is suppressed by
overpopulation.
<p>The definition of <a href="lex_s.htm#strictstilllife">strict still life</a> rules out such stable
patterns as the <a href="lex_b.htm#biblock">bi-block</a>. In such patterns there are dead cells
which have more than 3 neighbours in total, but fewer than 3 in any
component still life. These patterns are called pseudo still lifes,
and have been enumerated up to 32 bits, as shown in the table below.
<pre>
  --------------
  Bits    Number
  --------------
   8           1
   9           1
  10           7
  11          16
  12          55
  13         110
  14         279
  15         620
  16        1645
  17        4067
  18       10843
  19       27250
  20       70637
  21      179011
  22      462086
  23     1184882
  24     3068984
  25     7906676
  26    20463274
  27    52816265
  28   136655095
  29   353198379
  30   914075620
  31  2364815358
  32  6123084116
  --------------
</pre>
<p>Attribution of these counts is given in <a href="lex_s.htm#strictstilllife">strict still life</a>; see
also <a href="https://oeis.org/A056613">https://oeis.org/A056613</a>. The unique 32-bit <a href="lex_t.htm#triplepseudo">triple pseudo</a>
still life is included in the last count in the table. As the number
of bits increases, the pseudo still life count goes up exponentially
by approximately O(2.56<sup><i>n</i></sup>). By comparison, the rate for
<a href="lex_s.htm#strictstilllife">strict still lifes</a> is about O(2.46<sup><i>n</i></sup>) while for <a href="lex_q.htm#quasistilllife">quasi still lifes</a>
it's around O(3.04<sup><i>n</i></sup>).
<p>If a stable pattern's live cells plus its overpopulated dead cells
do not form a single mutually adjacent group, the pattern is usually
referred to as a <a href="lex_c.htm#constellation">constellation</a>. It is also a <a href="lex_s.htm#stilllife">still life</a> in the
general sense, but is neither "pseudo" nor "strict".
<p><a name=puffer>:</a><b>puffer</b> An object that moves like a <a href="lex_s.htm#spaceship">spaceship</a>, except that it leaves
debris behind. The first known puffers were found by Bill Gosper and
travelled at <i>c</i>/2 orthogonally (see diagram below for the very first
one, found in 1971).
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OOO......O.....O......OOO.$O..O.....OOO...OOO.....O..O$...O....OO.O...O.OO....O...$...O...................O...$...O..O.............O..O...$...O..OO...........OO..O...$..O...OO...........OO...O..$"
>.OOO......O.....O......OOO.
O..O.....OOO...OOO.....O..O
...O....OO.O...O.OO....O...
...O...................O...
...O..O.............O..O...
...O..OO...........OO..O...
..O...OO...........OO...O..
</a></pre></td></tr></table></center>
<p>Not long afterwards <i>c</i>/12 diagonal puffers were found (see
<a href="lex_s.htm#switchengine">switch engine</a>). Discounting <a href="lex_w.htm#wickstretcher">wickstretchers</a>, which are not
puffers in the conventional sense, no new velocity was obtained after
this until David Bell found the first <i>c</i>/3 orthogonal puffer in April
1996. Other new puffer speeds followed over the next several years.
<p>Many spaceships that travel orthogonally at a speed less than <i>c</i>/2
have useful side or back <a href="lex_s.htm#spark">sparks</a>. These can be used to perturb
<a href="lex_s.htm#standardspaceship">standard spaceships</a> that approach from behind. A common technique
for creating puffers for a new speed uses a <a href="lex_c.htm#convoy">convoy</a> of the new
spaceships to create debris from an approaching standard spaceship
such that a new standard spaceship is recreated on the same path as
the original one. This forms a closed loop, resulting in a
high-period puffer for the new speed.
<p>As of June 2018, puffers have been found matching every known
velocity of <a href="lex_e.htm#elementary">elementary</a> spaceship, except for <i>c</i>/6 and <i>c</i>/7 diagonal
and (2,1)<i>c</i>/6. It is also generally easy to create puffers based on
<a href="lex_m.htm#macrospaceship">macro-spaceships</a>, simply by removing some part of the trailing
cleanup mechanism.
<p><a name=pufferengine>:</a><b>puffer engine</b> A pattern which can be used as the main component of a
<a href="#puffer">puffer</a>. The pattern may itself be a puffer (e.g. the classic
<a href="#puffertrain">puffer train</a>), it may be a spaceship (e.g. the <a href="lex_s.htm#schickengine">Schick engine</a>), or
it may even be unstable (e.g. the <a href="lex_s.htm#switchengine">switch engine</a>).
<p><a name=pufferfish>:</a><b>pufferfish</b> (<i>c</i>/2, p12) A puffer discovered by Richard Schank in
November 2014, from a symmetric soup search using an early version of
<a href="lex_a.htm#apgsearch">apgsearch</a>. It consists of a pair of <a href="lex_b.htm#bheptomino">B-heptominoes</a> stabilised by
a backend that leaves only pairs of blocks behind. It is simple
enough to be easily synthesized with gliders.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:...O.......O...$..OOO.....OOO..$.OO..O...O..OO.$...OOO...OOO...$...............$....O.....O....$..O..O...O..O..$O.....O.O.....O$OO....O.O....OO$......O.O......$...O.O...O.O...$....O.....O....$"
>...O.......O...
..OOO.....OOO..
.OO..O...O..OO.
...OOO...OOO...
...............
....O.....O....
..O..O...O..O..
O.....O.O.....O
OO....O.O....OO
......O.O......
...O.O...O.O...
....O.....O....
</a></pre></td></tr></table></center>
See <a href="lex_s.htm#soup">soup</a> for a random initial pattern, generated by <a href="lex_a.htm#apgsearch">apgsearch</a> and
recorded in <a href="lex_c.htm#catagolue">Catagolue</a>, that produces a pufferfish.
<p><a name=pufferfishspaceship>:</a><b>pufferfish spaceship</b> (<i>c</i>/2, p36) Generally, any <a href="lex_s.htm#spaceship">spaceship</a>
constructed using <a href="#pufferfish">pufferfish</a>. May refer specifically to the
extensible <i>c</i>/2 <a href="lex_s.htm#spaceship">spaceship</a> constructed by Ivan Fomichev in December
2014, the first such spaceship to contain no period-2 or period-4
parts. (The first two or three rows might be considered to be period
2 or 4, but they are directly dependent on following rows for
support.).
<p>The pattern consists of two adjacent <a href="#pufferfish">pufferfish</a> <a href="#puffer">puffers</a>, plus
four copies of a nontrivial period 36 <i>c</i>/2 <a href="lex_f.htm#fuse">fuse</a> for pufferfish
<a href="lex_e.htm#exhaust">exhaust</a>, discovered using a randomized soup search.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.......O.......O..................O.......O........$......OOO.....OOO................OOO.....OOO.......$.....O..OO...OO..O..............OO.O.....O.OO......$.....O...O...O...O...............OO.O...O.OO.......$......OO.OO.OO.OO..............O.OO.......OO.O.....$......OO.O...O.OO.............O.O..O.O.O.O..O.O....$........O.....O...............O.O...OO.OO...O.O....$.........OO.OO.................OOO.O.....O.OOO.....$....OO..O.....O..OO.............OOO.......OOO......$....OO..O.....O..OO.............OO.........OO......$................................O...........O......$........O.O.O.O................OO...........OO.....$........OO...OO................OO...........OO.....$...................................................$...................................OO...OO.........$...................O..........O....OO...OO.........$...O..............OOO........OOO..............O....$..OOO...OO...O.O.OO.O.......OO.O.............OOO...$.OO..O..OO.........O........OOO.............OO.O...$.OOOO.O......O...O.O........OOO.............OO.....$OO.....O.......OO..OO.......OOOO..............OO...$.O................O..O......O..O...........O..OO...$.O.OOO..O....O.O..OO.......OO..............O....O..$.O.O...OO....O.O..OO...O....O.O...........O..O.O...$.OO......O..O.......O..O....OOO..........OO...OO...$O.....O.O....O.O....O.OO................O..........$.OO..O..O....O......O.OO............O....OO........$.OO...OO.......OO...OO.OO..OO......OOOOOO..........$........................O....O....O.O.O.O.......OOO$..............................O...O..O.........O...$..............................O....O..........O....$.............................O.................O.O.$"
>.......O.......O..................O.......O........
......OOO.....OOO................OOO.....OOO.......
.....O..OO...OO..O..............OO.O.....O.OO......
.....O...O...O...O...............OO.O...O.OO.......
......OO.OO.OO.OO..............O.OO.......OO.O.....
......OO.O...O.OO.............O.O..O.O.O.O..O.O....
........O.....O...............O.O...OO.OO...O.O....
.........OO.OO.................OOO.O.....O.OOO.....
....OO..O.....O..OO.............OOO.......OOO......
....OO..O.....O..OO.............OO.........OO......
................................O...........O......
........O.O.O.O................OO...........OO.....
........OO...OO................OO...........OO.....
...................................................
...................................OO...OO.........
...................O..........O....OO...OO.........
...O..............OOO........OOO..............O....
..OOO...OO...O.O.OO.O.......OO.O.............OOO...
.OO..O..OO.........O........OOO.............OO.O...
.OOOO.O......O...O.O........OOO.............OO.....
OO.....O.......OO..OO.......OOOO..............OO...
.O................O..O......O..O...........O..OO...
.O.OOO..O....O.O..OO.......OO..............O....O..
.O.O...OO....O.O..OO...O....O.O...........O..O.O...
.OO......O..O.......O..O....OOO..........OO...OO...
O.....O.O....O.O....O.OO................O..........
.OO..O..O....O......O.OO............O....OO........
.OO...OO.......OO...OO.OO..OO......OOOOOO..........
........................O....O....O.O.O.O.......OOO
..............................O...O..O.........O...
..............................O....O..........O....
.............................O.................O.O.
</a></pre></td></tr></table></center>
<p><a name=puffertrain>:</a><b>puffer train</b> The full name for a <a href="#puffer">puffer</a>, coined by Conway before
any examples were known. The term was also applied specifically to
the classic puffer train found by Bill Gosper and shown below. This
is very <a href="lex_d.htm#dirty">dirty</a>, and the tail does not stabilize until generation
5533. It consists of a <a href="lex_b.htm#bheptomino">B-heptomino</a> (shown here one generation
before the standard form) escorted by two <a href="lex_l.htm#lwss">LWSS</a>. (This was the
second known puffer. The first is shown under <a href="#puffer">puffer</a>.)
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.OOO...........OOO$O..O..........O..O$...O....OOO......O$...O....O..O.....O$..O....O........O.$"
>.OOO...........OOO
O..O..........O..O
...O....OOO......O
...O....O..O.....O
..O....O........O.
</a></pre></td></tr></table></center>
In April 2006, Jason Summers found a way to make the classic puffer
train into a p20 <a href="lex_s.htm#spaceship">spaceship</a> by adding a <a href="lex_g.htm#glider">glider</a> at the back:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:OOO...........OOO.$O..O..........O..O$O......OOO....O...$O.....O..O....O...$.O.O..O...O....O.O$.......OOOO.......$.........O........$..................$..................$..................$.......OOO........$.......O..........$........O.........$"
>OOO...........OOO.
O..O..........O..O
O......OOO....O...
O.....O..O....O...
.O.O..O...O....O.O
.......OOOO.......
.........O........
..................
..................
..................
.......OOO........
.......O..........
........O.........
</a></pre></td></tr></table></center>
<p><a name=puffsuppressor>:</a><b>puff suppressor</b> An attachment at the back of a <a href="lex_l.htm#linepuffer">line puffer</a> that
suppresses all or some of its puffing action. The example below (by
Hartmut Holzwart) has a 3-cell puff suppressor at the back which
suppresses the entire puff, making a p2 <a href="lex_s.htm#spaceship">spaceship</a>. If you delete
this puff suppressor then you get a p60 double <a href="lex_b.htm#beehive">beehive</a> <a href="#puffer">puffer</a>.
Puff suppressors were first recognised by Alan Hensel in April 1994.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:............O....................$..........OO.O...................$..........OO...O.................$........O...OO.O.....O...........$........OOOO.OO...OOOO.......O.O.$......O......O....OOO.....O.O..O.$......OOOOOOO...O...O....O..O....$...O.O......OO..O...O.O.OO....O..$..OOOOOOOOO.....O..OO........O...$.OO..............O.OO.OOOO...O..O$OO....OO.O..........O...O..O.O...$.OO....O........OOO......O.O.O..O$.........O......OO......O....OO..$.OO....O........OOO......O.O.O..O$OO....OO.O..........O...O..O.O...$.OO..............O.OO.OOOO...O..O$..OOOOOOOOO.....O..OO........O...$...O.O......OO..O...O.O.OO....O..$......OOOOOOO...O...O....O..O....$......O......O....OOO.....O.O..O.$........OOOO.OO...OOOO.......O.O.$........O...OO.O.....O...........$..........OO...O.................$..........OO.O...................$............O....................$"
>............O....................
..........OO.O...................
..........OO...O.................
........O...OO.O.....O...........
........OOOO.OO...OOOO.......O.O.
......O......O....OOO.....O.O..O.
......OOOOOOO...O...O....O..O....
...O.O......OO..O...O.O.OO....O..
..OOOOOOOOO.....O..OO........O...
.OO..............O.OO.OOOO...O..O
OO....OO.O..........O...O..O.O...
.OO....O........OOO......O.O.O..O
.........O......OO......O....OO..
.OO....O........OOO......O.O.O..O
OO....OO.O..........O...O..O.O...
.OO..............O.OO.OOOO...O..O
..OOOOOOOOO.....O..OO........O...
...O.O......OO..O...O.O.OO....O..
......OOOOOOO...O...O....O..O....
......O......O....OOO.....O.O..O.
........OOOO.OO...OOOO.......O.O.
........O...OO.O.....O...........
..........OO...O.................
..........OO.O...................
............O....................
</a></pre></td></tr></table></center>
<p><a name=pull>:</a><b>pull</b> A reaction, most often mediated by gliders, that moves an object
closer to the source of the reaction. See <a href="lex_b.htm#blockpull">block pull</a>,
<a href="lex_b.htm#blinkerpull">blinker pull</a>, <a href="lex_l.htm#loafpull">loaf pull</a>; also <a href="lex_e.htm#elbow">elbow</a>.
<p><a name=pulsar>:</a><b>pulsar</b> (p3) Despite its size, this is the fourth most common
<a href="lex_o.htm#oscillator">oscillator</a> (and by far the most common of period greater than 2)
and was found very early on by Conway. See also <a href="#prepulsar">pre-pulsar</a>,
<a href="#pulsarquadrant">pulsar quadrant</a>, and <a href="lex_q.htm#quasar">quasar</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..OOO...OOO..$.............$O....O.O....O$O....O.O....O$O....O.O....O$..OOO...OOO..$.............$..OOO...OOO..$O....O.O....O$O....O.O....O$O....O.O....O$.............$..OOO...OOO..$"
>..OOO...OOO..
.............
O....O.O....O
O....O.O....O
O....O.O....O
..OOO...OOO..
.............
..OOO...OOO..
O....O.O....O
O....O.O....O
O....O.O....O
.............
..OOO...OOO..
</a></pre></td></tr></table></center>
<p><a name=pulsar182220>:</a><b>pulsar 18-22-20</b> = <a href="lex_t.htm#twopulsarquadrants">two pulsar quadrants</a>
<p><a name=pulsarcp485672>:</a><b>pulsar CP 48-56-72</b> = <a href="#pulsar">pulsar</a> (The numbers refer to the populations
of the three <a href="#phase">phases</a>.)
<p><a name=pulsarpixeldisplay>:</a><b>Pulsar Pixel Display</b> (p30 circuitry) A large-scale raster line
display device constructed by Mark Walsh in August 2010, where
<a href="#pulsar">pulsars</a> form the individual pixels in an otherwise empty grid. The
published sample pattern displays and erases eight 7x5-pixel
characters on each of two lines of text.
<p><a name=pulsarquadrant>:</a><b>pulsar quadrant</b> (p3) This consists of a quarter of the outer part of
a <a href="#pulsar">pulsar</a> stabilized by a <a href="lex_c.htm#cisfusewithtwotails">cis fuse with two tails</a>. This is
reminiscent of <a href="lex_m.htm#mold">mold</a> and <a href="lex_j.htm#jam">jam</a>. Found by Dave Buckingham in July
1973. See also <a href="lex_t.htm#twopulsarquadrants">two pulsar quadrants</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....O..$...OOO..$..O...OO$O..O..O.$O...O.O.$O....O..$........$..OOO...$"
>.....O..
...OOO..
..O...OO
O..O..O.
O...O.O.
O....O..
........
..OOO...
</a></pre></td></tr></table></center>
<p><a name=pulse>:</a><b>pulse</b> A moving object, such as a <a href="lex_s.htm#spaceship">spaceship</a> or <a href="lex_h.htm#herschel">Herschel</a>, which can
be used to transmit information. See <a href="#pulsedivider">pulse divider</a>.
<p>Also another name for a <a href="#pulsarquadrant">pulsar quadrant</a>.
<p><a name=pulsedivider>:</a><b>pulse divider</b> A mechanism that lets every <i>n</i>-th object that reaches it
pass through, and deletes all the rest, where <i>n</i> &gt; 1 and the objects
are typically <a href="lex_g.htm#glider">gliders</a>, <a href="lex_s.htm#spaceship">spaceships</a> or <a href="lex_h.htm#herschel">Herschels</a>. A common
synonym is <a href="#periodmultiplier">period multiplier</a>. For <i>n</i>=2, the simplest known stable
pulse dividers are the <a href="lex_s.htm#semisnark">semi-Snarks</a>.
<p>The following diagram shows a p5 glider pulse divider by Dieter
Leithner (February 1998). The first glider moves the centre block
and is reflected at 90 degrees. The next glider to come along will
not be reflected, but will move the block back to its original
position. The relatively small size and low period of this example
made it useful for constructing compact glider <a href="lex_g.htm#gun">guns</a> of certain
periods, but it became largely obsolete with the discovery of the
<a href="lex_s.htm#stable">stable</a> <a href="lex_c.htm#ccsemisnark">CC semi-Snark</a>, which uses the same basic mechanism.
Period 7, 22, 36 and 46 versions of this pulse divider are also
known.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.....OO...................$.....OO...................$..........................$..................OO......$.................O..O.....$.................O.O..O..O$O...............OO.O.OOOOO$.OO...........O...OO......$OO...............OO..OOO..$.............O...O.O..O.O.$........OO.......OO..OO.O.$........OO....O...OO...O..$................OO.O.OO...$.................O.O.O....$.................O.O..O...$..................O..OO...$..OO......................$...O......................$OOO.......................$O.........................$..........................$............OO............$............O.............$.............OOO..........$...............O..........$"
>.....OO...................
.....OO...................
..........................
..................OO......
.................O..O.....
.................O.O..O..O
O...............OO.O.OOOOO
.OO...........O...OO......
OO...............OO..OOO..
.............O...O.O..O.O.
........OO.......OO..OO.O.
........OO....O...OO...O..
................OO.O.OO...
.................O.O.O....
.................O.O..O...
..................O..OO...
..OO......................
...O......................
OOO.......................
O.........................
..........................
............OO............
............O.............
.............OOO..........
...............O..........
</a></pre></td></tr></table></center>
<p><a name=pulshuttlev>:</a><b>pulshuttle V</b> (p30) Found by Robert Wainwright, May 1985. Compare
<a href="lex_e.htm#eureka">Eureka</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.............O..............O.............$............O.O.......O....O.O............$.............O......OO.OO...O.............$......................O...................$..OO......OO..................OO......OO..$O....O..O....O..............O....O..O....O$O....O..O....O..............O....O..O....O$O....O..O....O........O.....O....O..O....O$..OO......OO........OO.OO.....OO......OO..$......................O...................$..........................................$..........................................$..OO......OO..................OO......OO..$O....O..O....O........O.....O....O..O....O$O....O..O....O......OO.OO...O....O..O....O$O....O..O....O........O.....O....O..O....O$..OO......OO..................OO......OO..$..........................................$..........................................$......................O...................$..OO......OO........OO.OO.....OO......OO..$O....O..O....O........O.....O....O..O....O$O....O..O....O..............O....O..O....O$O....O..O....O..............O....O..O....O$..OO......OO..................OO......OO..$......................O...................$.............O......OO.OO...O.............$............O.O.......O....O.O............$.............O..............O.............$"
>.............O..............O.............
............O.O.......O....O.O............
.............O......OO.OO...O.............
......................O...................
..OO......OO..................OO......OO..
O....O..O....O..............O....O..O....O
O....O..O....O..............O....O..O....O
O....O..O....O........O.....O....O..O....O
..OO......OO........OO.OO.....OO......OO..
......................O...................
..........................................
..........................................
..OO......OO..................OO......OO..
O....O..O....O........O.....O....O..O....O
O....O..O....O......OO.OO...O....O..O....O
O....O..O....O........O.....O....O..O....O
..OO......OO..................OO......OO..
..........................................
..........................................
......................O...................
..OO......OO........OO.OO.....OO......OO..
O....O..O....O........O.....O....O..O....O
O....O..O....O..............O....O..O....O
O....O..O....O..............O....O..O....O
..OO......OO..................OO......OO..
......................O...................
.............O......OO.OO...O.............
............O.O.......O....O.O............
.............O..............O.............
</a></pre></td></tr></table></center>
<p><a name=pureglidergenerator>:</a><b>pure glider generator</b> A pattern that evolves into one or more
<a href="lex_g.htm#glider">gliders</a>, and nothing else. There was some interest in these early
on, but they are no longer considered important. Here's a neat
example:
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..O............$..O............$OOO............$...............$......OOO......$.......O.......$............OOO$............O..$............O..$"
>..O............
..O............
OOO............
...............
......OOO......
.......O.......
............OOO
............O..
............O..
</a></pre></td></tr></table></center>
<p><a name=push>:</a><b>push</b> A reaction that moves an object farther away from the source of
the reaction. See <a href="lex_s.htm#slidingblockmemory">sliding block memory</a>, <a href="#picalculator">pi calculator</a>, <a href="lex_e.htm#elbow">elbow</a>,
<a href="lex_u.htm#universalconstructor">universal constructor</a>. See also <a href="#pull">pull</a>, <a href="lex_f.htm#fire">fire</a>.
<p><a name=pushalong>:</a><b>pushalong</b> Any <a href="lex_t.htm#tagalong">tagalong</a> at the front of a spaceship. The following
is an example found by David Bell in 1992, attached to the front of a
<a href="lex_m.htm#mwss">MWSS</a>.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:..OOO.O.....$.OOOO.O.....$OO..........$.O.O........$..OOOO.O....$...OOO......$............$............$......OOOOO.$......O....O$......O.....$.......O...O$.........O..$"
>..OOO.O.....
.OOOO.O.....
OO..........
.O.O........
..OOOO.O....
...OOO......
............
............
......OOOOO.
......O....O
......O.....
.......O...O
.........O..
</a></pre></td></tr></table></center>
<p><a name=pyrotechnecium>:</a><b>pyrotechnecium</b> (p8) Found by Dave Buckingham in 1972.
<center><table cellspacing=0 cellpadding=0><tr><td><pre><a href="lexpatt:.......O........$.....OOOOO......$....O.....O.....$.O..O.O.OO.O....$O.O.O.O....O..O.$.O..O....O.O.O.O$....O.OO.O.O..O.$.....O.....O....$......OOOOO.....$........O.......$"
>.......O........
.....OOOOO......
....O.....O.....
.O..O.O.OO.O....
O.O.O.O....O..O.
.O..O....O.O.O.O
....O.OO.O.O..O.
.....O.....O....
......OOOOO.....
........O.......
</a></pre></td></tr></table></center>
<p><a name=pyrotechneczum>:</a><b>pyrotechneczum</b> A common mistaken spelling of <a href="#pyrotechnecium">pyrotechnecium</a>, caused
by a copying error in the early 1990s.
<p><a name=python>:</a><b>python</b> = <a href="lex_l.htm#longsnake">long snake</a>
<hr>
<center>
<b>
<a href="lex_1.htm">1-9</a> |
<a href="lex_a.htm">A</a> |
<a href="lex_b.htm">B</a> |
<a href="lex_c.htm">C</a> |
<a href="lex_d.htm">D</a> |
<a href="lex_e.htm">E</a> |
<a href="lex_f.htm">F</a> |
<a href="lex_g.htm">G</a> |
<a href="lex_h.htm">H</a> |
<a href="lex_i.htm">I</a> |
<a href="lex_j.htm">J</a> |
<a href="lex_k.htm">K</a> |
<a href="lex_l.htm">L</a> |
<a href="lex_m.htm">M</a> |
<a href="lex_n.htm">N</a> |
<a href="lex_o.htm">O</a> |
<a href="lex_p.htm">P</a> |
<a href="lex_q.htm">Q</a> |
<a href="lex_r.htm">R</a> |
<a href="lex_s.htm">S</a> |
<a href="lex_t.htm">T</a> |
<a href="lex_u.htm">U</a> |
<a href="lex_v.htm">V</a> |
<a href="lex_w.htm">W</a> |
<a href="lex_x.htm">X</a> |
<a href="lex_y.htm">Y</a> |
<A href="lex_z.htm">Z</A></b>

</center>
<hr>
</body>