A284181 Decimal representation of the x-axis, from the left edge to the origin, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 813", based on the 5-celled von Neumann neighborhood.

1, 2, 5, 10, 23, 47, 87, 171, 381, 766, 1407, 2751, 6111, 12287, 22527, 44031, 97791, 196607, 360447, 704511, 1564671, 3145727, 5767167, 11272191, 25034751, 50331647, 92274687, 180355071, 400556031, 805306367, 1476395007, 2885681151, 6408896511, 12884901887

Offset

0,2

Comments

Initialized with a single black (ON) cell at stage zero.

References

S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.

Links

Robert Price, Table of n, a(n) for n = 0..126

Robert Price, Diagrams of first 20 stages

N. J. A. Sloane, On the Number of ON Cells in Cellular Automata, arXiv:1503.01168 [math.CO], 2015

Eric Weisstein's World of Mathematics, Elementary Cellular Automaton

S. Wolfram, A New Kind of Science

Wolfram Research, Wolfram Atlas of Simple Programs

Index entries for sequences related to cellular automata

Index to 2D 5-Neighbor Cellular Automata

Index to Elementary Cellular Automata

Formula

Conjectures from Colin Barker, Mar 22 2017: (Start)

G.f.: (1 + x + 3*x^2 + 5*x^3 - 3*x^4 + 8*x^5 - 8*x^6 + 4*x^7 + 2*x^8 + x^9 + x^10 + 16*x^13 - 16*x^14) / ((1 - x)*(1 - 2*x)*(1 + 2*x)*(1 + 4*x^2)).

a(n) = a(n-1) + 16*a(n-4) - 16*a(n-5) for n>10.

(End)

Mathematica

CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code = 813; stages = 128;
rule = IntegerDigits[code, 2, 10];
g = 2 * stages + 1; (* Maximum size of grid *)
a = PadLeft[{{1}}, {g, g}, 0, Floor[{g, g}/2]]; (* Initial ON cell on grid *)
ca = a;
ca = Table[ca = CAStep[rule, ca], {n, 1, stages + 1}];
PrependTo[ca, a];
(* Trim full grid to reflect growth by one cell at each stage *)
k = (Length[ca[[1]]] + 1)/2;
ca = Table[Table[Part[ca[[n]] [[j]], Range[k + 1 - n, k - 1 + n]], {j, k + 1 - n, k - 1 + n}], {n, 1, k}];
Table[FromDigits[Part[ca[[i]] [[i]], Range[1, i]], 2], {i, 1, stages - 1}]

Crossrefs

Cf. A284179, A284180, A284182.

Sequence in context: A026677 A109165 A018344 * A365376 A291249 A365441

Adjacent sequences: A284178 A284179 A284180 * A284182 A284183 A284184

Keyword

nonn,easy

Author

Robert Price, Mar 21 2017

Status

approved