cp's OEIS Frontend

A283505 Binary 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 641", based on the 5-celled von Neumann neighborhood.

%I A283505 #10 Feb 16 2025 08:33:42
%S A283505 1,0,101,11,10111,1111,1011111,111111,101111111,11111111,10111111111,
%T A283505 1111111111,1011111111111,111111111111,101111111111111,11111111111111,
%U A283505 10111111111111111,1111111111111111,1011111111111111111,111111111111111111,101111111111111111111
%N A283505 Binary 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 641", based on the 5-celled von Neumann neighborhood.
%C A283505 Initialized with a single black (ON) cell at stage zero.
%D A283505 S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
%H A283505 Robert Price, <a href="/A283505/b283505.txt">Table of n, a(n) for n = 0..126</a>
%H A283505 Robert Price, <a href="/A283505/a283505.tmp.txt">Diagrams of first 20 stages</a>
%H A283505 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 A283505 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A283505 S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H A283505 Wolfram Research, <a href="http://atlas.wolfram.com/">Wolfram Atlas of Simple Programs</a>
%H A283505 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A283505 <a href="https://oeis.org/wiki/Index_to_2D_5-Neighbor_Cellular_Automata">Index to 2D 5-Neighbor Cellular Automata</a>
%H A283505 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%F A283505 Conjectures from _Colin Barker_, Mar 10 2017: (Start)
%F A283505 G.f.: (1 - x + x^2 + 10*x^3) / ((1 - x)*(1 - 10*x)*(1 + 10*x)).
%F A283505 a(n) = -1/9 + (-5)^n*2^(n-1) + 23*2^n*5^(n-1)/9 for n>1.
%F A283505 a(n) = a(n-1) + 100*a(n-2) - 100*a(n-3) for n>3.
%F A283505 (End)
%t A283505 CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0},{2, 1, 2}, {0, 2, 0}}, a, 2],{2}];
%t A283505 code = 641; stages = 128;
%t A283505 rule = IntegerDigits[code, 2, 10];
%t A283505 g = 2 * stages + 1; (* Maximum size of grid *)
%t A283505 a = PadLeft[{{1}}, {g, g}, 0,Floor[{g, g}/2]]; (* Initial ON cell on grid *)
%t A283505 ca = a;
%t A283505 ca = Table[ca = CAStep[rule, ca], {n, 1, stages + 1}];
%t A283505 PrependTo[ca, a];
%t A283505 (* Trim full grid to reflect growth by one cell at each stage *)
%t A283505 k = (Length[ca[[1]]] + 1)/2;
%t A283505 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 A283505 Table[FromDigits[Part[ca[[i]] [[i]], Range[i, 2 * i - 1]], 10], {i, 1, stages - 1}]
%Y A283505 Cf. A283504, A283506, A283507.
%K A283505 nonn,easy
%O A283505 0,3
%A A283505 _Robert Price_, Mar 09 2017