This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A188343 #7 Mar 31 2012 13:22:29 %S A188343 0,1,9,13,41,45,73,85,169,173,201,213,297,317,441,485,681,685,713,725, %T A188343 809,829,953,997,1193,1213,1353,1397,1689,1773,2201,2309,2737,2765, %U A188343 2817,2845,2953,2989,3113 %N A188343 Number of "ON" cells at n-th stage in simple 2-dimensional cellular automaton (see Comments for precise definition). %C A188343 On the infinite square grid, we start at stage 0 with all square cells in the OFF state. %C A188343 At stage 1 we turn ON a single cell in the central position. %C A188343 For n>1, if n is even, at stage n we turn ON all the OFF neighboring cells from cells that were turned ON at stage n-1. %C A188343 For n>1, if n is odd, at stage n we turn ON all the OFF cells that have exactly one neighbor that was turned ON at stage n-1. %C A188343 First differs from A160118 at a(13). %H A188343 Nathaniel Johnston, <a href="/A188343/a188343.png">13th generation of this sequence</a>, where it first differs from A160118. Cells in green were newly turned on in generation 13 and are also turned on in generation 13 of A160118. Cells in red are newly turned on but are not turned on in A160118. %H A188343 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a> %F A188343 For n even, use Generations rule "/12345678/250". For n odd, use Generations rule "/1/250". %Y A188343 Cf. A160118. %K A188343 nonn %O A188343 0,3 %A A188343 _Nathaniel Johnston_, Mar 28 2011