cp's OEIS Frontend

A290191 Binary representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 673", based on the 5-celled von Neumann neighborhood.

%I A290191 #14 Feb 16 2025 08:33:49
%S A290191 1,10,111,1110,11111,111110,1111111,11111110,111111111,1111111110,
%T A290191 11111111111,111111111110,1111111111111,11111111111110,
%U A290191 111111111111111,1111111111111110,11111111111111111,111111111111111110,1111111111111111111,11111111111111111110
%N A290191 Binary representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 673", based on the 5-celled von Neumann neighborhood.
%C A290191 Initialized with a single black (ON) cell at stage zero.
%D A290191 S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
%H A290191 Robert Price, <a href="/A290191/b290191.txt">Table of n, a(n) for n = 0..126</a>
%H A290191 Robert Price, <a href="/A290191/a290191.tmp.txt">Diagrams of first 20 stages</a>
%H A290191 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 A290191 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A290191 S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H A290191 Wolfram Research, <a href="http://atlas.wolfram.com/">Wolfram Atlas of Simple Programs</a>
%H A290191 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A290191 <a href="https://oeis.org/wiki/Index_to_2D_5-Neighbor_Cellular_Automata">Index to 2D 5-Neighbor Cellular Automata</a>
%H A290191 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%F A290191 Conjecture: a(n) is the binary representation of 2^(n - 1) - 1 - (n mod 2).
%t A290191 CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0},{2, 1, 2}, {0, 2, 0}}, a, 2],{2}];
%t A290191 code = 673; stages = 128;
%t A290191 rule = IntegerDigits[code, 2, 10];
%t A290191 g = 2 * stages + 1; (* Maximum size of grid *)
%t A290191 a = PadLeft[{{1}}, {g, g}, 0,Floor[{g, g}/2]]; (* Initial ON cell on grid *)
%t A290191 ca = a;
%t A290191 ca = Table[ca = CAStep[rule, ca], {n, 1, stages + 1}];
%t A290191 PrependTo[ca, a];
%t A290191 (* Trim full grid to reflect growth by one cell at each stage *)
%t A290191 k = (Length[ca[[1]]] + 1)/2;
%t A290191 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 A290191 Table[FromDigits[Part[ca[[i]] [[i]], Range[i, 2 * i - 1]], 10], {i, 1, stages - 1}]
%Y A290191 Cf. A288335, A140253, A140252.
%K A290191 nonn,easy
%O A290191 0,2
%A A290191 _Robert Price_, Jul 23 2017