A281216 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 342", based on the 5-celled von Neumann neighborhood.

1, 3, 4, 14, 17, 59, 68, 238, 273, 955, 1092, 3822, 4369, 15291, 17476, 61166, 69905, 244667, 279620, 978670, 1118481, 3914683, 4473924, 15658734, 17895697, 62634939, 71582788, 250539758, 286331153, 1002159035, 1145324612, 4008636142, 4581298449, 16034544571

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, Jan 18 2017: (Start)

a(n) = 4*a(n-2) + a(n-4) - 4*a(n-6) for n>5.

G.f.: (1+3*x+2*x^3) / ((1-x)*(1+x)*(1-2*x)*(1+2*x)*(1+x^2)).

(End)

Mathematica

CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code = 342; 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. A281214, A281215, A281217.

Sequence in context: A281737 A281108 A281310 * A282307 A282604 A281524

Adjacent sequences: A281213 A281214 A281215 * A281217 A281218 A281219

Keyword

nonn,easy

Author

Robert Price, Jan 17 2017

Status

approved