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 A246310 #15 Mar 17 2015 23:49:45
%S A246310 1,8,8,25,4,32,32,100,25,61,88,208,112,164,232,380,188,304,341,596,
%T A246310 437,576,528,696,553,749,736,924,1016,1060,1161,1372,1200,1388,1456,
%U A246310 1720,1493,1761,1660,2072,1781,2084,1973,2732,2252,2596,2552,3121,2684,3145,2972,3828,3132,3588,3480,4061,3772,4073,4009,4929,4264,4996,4845,5493,5160,5804,5156
%N A246310 Number of ON cells at generation n of 2-D cellular automaton in which a cell is ON iff either 1 or 4 of its eight neighbors were ON at previous generation, starting with a single ON cell.
%C A246310 This is the Rule 780 outer totalistic 8-neighbor 2-D CA.
%C A246310 The first few generations are easy to understand, but then there are complications (hence the keyword "look", which refers to the illustrations).
%H A246310 N. J. A. Sloane, <a href="/A246310/a246310.pdf">Illustration of first 28 generations.</a>
%H A246310 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
%t A246310 Total@*Total /@ CellularAutomaton[{780, {2, {{2, 2, 2}, {2, 1, 2}, {2, 2, 2}}}, {1, 1}}, {{{1}}, 0}, 66]
%t A246310 ArrayPlot /@ CellularAutomaton[{780, {2, {{2, 2, 2}, {2, 1, 2}, {2, 2, 2}}}, {1, 1}}, {{{1}}, 0}, 28]
%Y A246310 Cf. A253086 (5-celled analog).
%K A246310 nonn,look
%O A246310 0,2
%A A246310 _N. J. A. Sloane_, Aug 23 2014