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%I #13 Aug 23 2014 13:23:25
%S 1,8,20,28,56,52,124,64,184,128,304,136,312,276,544,260,472,496,796,
%T 404,720,720,1220,540,972,840,1724,808,1356,1268,2056,1264,1740,1772,
%U 2608,1392,2308,1980,3148,2108,2728,2724,3776,2408,3276,3200,4196,3128,3872,3768,5360,3408,4472,4720,5720,4344,5380,5144,6788,5004,5836,6168,7508,5704,7104,6620,8916
%N Number of ON cells at generation n of 2-D cellular automaton in which a cell is ON iff either 1, 2 or 3 of its eight neighbors were ON at previous generation, starting with a single ON cell.
%C This is the Rule 252 outer totalistic 8-neighbor 2-D CA.
%C The first few generations are easy to understand, but then there are complications (hence the keyword "look", which refers to the illustrations).
%H N. J. A. Sloane, <a href="/A246308/a246308.pdf">Illustration of first 28 generations.</a>
%t Total@*Total /@ CellularAutomaton[{252, {2, {{2, 2, 2}, {2, 1, 2}, {2, 2, 2}}}, {1, 1}}, {{{1}}, 0}, 66]
%t ArrayPlot /@ CellularAutomaton[{252, {2, {{2, 2, 2}, {2, 1, 2}, {2, 2, 2}}}, {1, 1}}, {{{1}}, 0}, 28]
%K nonn,look
%O 0,2
%A _N. J. A. Sloane_, Aug 23 2014