A283584 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 646", based on the 5-celled von Neumann neighborhood.

1, 3, 5, 11, 21, 43, 69, 219, 261, 795, 1301, 2923, 5205, 11691, 20805, 46811, 83205, 187163, 333077, 748395, 1332309, 2993579, 5329221, 11974363, 21316869, 47897371, 85267733, 191589227, 341070933, 766356907, 1364283717, 3065427675, 5457134853, 12261710619

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 12 2017: (Start)

G.f.: (1 + 3*x + x^2 - x^3 + x^4 - x^5 - 15*x^6 + 47*x^7 - 16*x^8 - 84*x^9 + 256*x^10 - 256*x^11) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 + 2*x)*(1 + x^2)*(1 + x^4)).

a(n) = 4*a(n-2) + a(n-8) - 4*a(n-10) for n>11.

(End)

Mathematica

CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code = 646; 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[i, 2 * i - 1]], 2], {i , 1, stages - 1}]

Crossrefs

Cf. A283581, A283582, A283583.

Sequence in context: A146042 A291219 A284358 * A283702 A284539 A154917

Adjacent sequences: A283581 A283582 A283583 * A283585 A283586 A283587

Keyword

nonn,easy

Author

Robert Price, Mar 11 2017

Status

approved