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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.

A288700 Decimal representation of the diagonal from the origin to the corner of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 494", based on the 5-celled von Neumann neighborhood.

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%I A288700 #8 Feb 16 2025 08:33:48
%S A288700 1,2,0,8,8,32,32,128,128,512,512,2048,2048,8192,8192,32768,32768,
%T A288700 131072,131072,524288,524288,2097152,2097152,8388608,8388608,33554432,
%U A288700 33554432,134217728,134217728,536870912,536870912,2147483648,2147483648,8589934592
%N A288700 Decimal representation of the diagonal from the origin to the corner of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 494", based on the 5-celled von Neumann neighborhood.
%C A288700 Initialized with a single black (ON) cell at stage zero.
%D A288700 S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
%H A288700 Robert Price, <a href="/A288700/b288700.txt">Table of n, a(n) for n = 0..126</a>
%H A288700 Robert Price, <a href="/A288700/a288700.tmp.txt">Diagrams of first 20 stages</a>
%H A288700 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 [math.CO], 2015
%H A288700 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A288700 S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H A288700 Wolfram Research, <a href="http://atlas.wolfram.com/">Wolfram Atlas of Simple Programs</a>
%H A288700 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A288700 <a href="https://oeis.org/wiki/Index_to_2D_5-Neighbor_Cellular_Automata">Index to 2D 5-Neighbor Cellular Automata</a>
%H A288700 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%t A288700 CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0},{2, 1, 2}, {0, 2, 0}}, a, 2],{2}];
%t A288700 code = 494; stages = 128;
%t A288700 rule = IntegerDigits[code, 2, 10];
%t A288700 g = 2 * stages + 1; (* Maximum size of grid *)
%t A288700 a = PadLeft[{{1}}, {g, g}, 0,Floor[{g, g}/2]]; (* Initial ON cell on grid *)
%t A288700 ca = a;
%t A288700 ca = Table[ca = CAStep[rule, ca], {n, 1, stages + 1}];
%t A288700 PrependTo[ca, a];
%t A288700 (* Trim full grid to reflect growth by one cell at each stage *)
%t A288700 k = (Length[ca[[1]]] + 1)/2;
%t A288700 ca = Table[Table[Part[ca[[n]] [[j]],Range[k + 1 - n, k - 1 + n]], {j, k + 1 - n, k - 1 + n}], {n, 1, k}];
%t A288700 Table[FromDigits[Part[ca[[i]] [[i]], Range[i, 2 * i - 1]], 10], {i, 1, stages - 1}]
%Y A288700 Cf. A288697, A288697, A288699.
%K A288700 nonn,easy
%O A288700 0,2
%A A288700 _Robert Price_, Jun 13 2017