A283355 Binary 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 621", based on the 5-celled von Neumann neighborhood.

1, 10, 100, 1011, 10001, 101110, 1000110, 10111110, 100011110, 1011111110, 10001111110, 101111111110, 1000111111110, 10111111111110, 100011111111110, 1011111111111110, 10001111111111110, 101111111111111110, 1000111111111111110, 10111111111111111110

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 06 2017: (Start)

G.f.: (1 + 9*x - 10*x^2 + 11*x^3 - 10*x^4 + 9*x^5 + 100*x^7) / ((1 - x)*(1 - 10*x)*(1 + 10*x)).

a(n) = (-20000 - 99*(-10)^n + 18101*10^n) / 18000 for n>4.

a(n) = a(n-1) + 100*a(n-2) - 100*a(n-3) for n>5.

(End)

Mathematica

CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code = 621; 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]], 10], {i, 1, stages - 1}]

Crossrefs

Cf. A283356, A283357, A283358.

Sequence in context: A283291 A283387 A283404 * A319418 A283171 A283252

Adjacent sequences: A283352 A283353 A283354 * A283356 A283357 A283358

Keyword

nonn,easy

Author

Robert Price, Mar 05 2017

Status

approved