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 A253089 #15 Mar 17 2015 23:49:46
%S A253089 1,9,20,29,69,44,112,84,228,81,253,240,361,329,408,436,552,544,656,
%T A253089 852,748,752,1040,1173,1097,928,1389,1857,1208,1244,1664,2457,1448,
%U A253089 1636,2028,2732,2164,1957,2841,3204,2849,2301,3504,3869,3548,2756,4140,4509,4060,3388
%N A253089 Number of ON cells at generation n of 9-celled totalistic CA defined by Rule 510.
%H A253089 N. J. A. Sloane, <a href="/A253089/a253089.png">Illustration of generations 0-15</a>
%H A253089 N. J. A. Sloane, <a href="http://arxiv.org/abs/1503.01168">On the Number of ON Cells in Cellular Automata</a>, arXiv:1503.01168, 2015
%H A253089 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%F A253089 It would be nice to have a recurrence.
%t A253089 Map[Function[Apply[Plus, Flatten[#1]]],
%t A253089 CellularAutomaton[{510, {2, {{2, 2, 2}, {2, 1, 2}, {2, 2, 2}}}, {1, 1}}, {{{1}}, 0}, 66]]
%t A253089 ArrayPlot /@ CellularAutomaton[{510, {2, {{2, 2, 2}, {2, 1, 2}, {2, 2, 2}}}, {1, 1}}, {{{1}}, 0}, 15]
%Y A253089 Cf. A169699 (5-neighbor analog).
%K A253089 nonn
%O A253089 0,2
%A A253089 _N. J. A. Sloane_, Feb 12 2015