cp's OEIS Frontend

A281421 Decimal representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 366", based on the 5-celled von Neumann neighborhood.

%I A281421 #9 Feb 16 2025 08:33:39
%S A281421 1,3,3,15,11,63,43,255,171,1023,683,4095,2731,16383,15019,57343,19115,
%T A281421 131071,437931,254975,764587,4055039,314027,1998847,6498987,19529727,
%U A281421 134131371,108258303,528132779,356507647,2144062123,1535082495,8240704171,4595515391
%N A281421 Decimal representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 366", based on the 5-celled von Neumann neighborhood.
%C A281421 Initialized with a single black (ON) cell at stage zero.
%D A281421 S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
%H A281421 Robert Price, <a href="/A281421/b281421.txt">Table of n, a(n) for n = 0..126</a>
%H A281421 Robert Price, <a href="/A281421/a281421.tmp.txt">Diagrams of first 20 stages</a>
%H A281421 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 A281421 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A281421 S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H A281421 Wolfram Research, <a href="http://atlas.wolfram.com/">Wolfram Atlas of Simple Programs</a>
%H A281421 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A281421 <a href="https://oeis.org/wiki/Index_to_2D_5-Neighbor_Cellular_Automata">Index to 2D 5-Neighbor Cellular Automata</a>
%H A281421 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%t A281421 CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0},{2, 1, 2}, {0, 2, 0}}, a, 2],{2}];
%t A281421 code = 366; stages = 128;
%t A281421 rule = IntegerDigits[code, 2, 10];
%t A281421 g = 2 * stages + 1; (* Maximum size of grid *)
%t A281421 a = PadLeft[{{1}}, {g, g}, 0,Floor[{g, g}/2]]; (* Initial ON cell on grid *)
%t A281421 ca = a;
%t A281421 ca = Table[ca = CAStep[rule, ca], {n, 1, stages + 1}];
%t A281421 PrependTo[ca, a];
%t A281421 (* Trim full grid to reflect growth by one cell at each stage *)
%t A281421 k = (Length[ca[[1]]] + 1)/2;
%t A281421 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 A281421 Table[FromDigits[Part[ca[[i]] [[i]], Range[i, 2 * i - 1]], 2], {i ,1, stages - 1}]
%Y A281421 Cf. A281418, A281419, A281420.
%K A281421 nonn,easy
%O A281421 0,2
%A A281421 _Robert Price_, Jan 21 2017