A282803 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 507", based on the 5-celled von Neumann neighborhood.

1, 2, 7, 2, 31, 10, 127, 42, 511, 170, 2047, 682, 8191, 2730, 32767, 10922, 131071, 43690, 524287, 174762, 2097151, 699050, 8388607, 2796202, 33554431, 11184810, 134217727, 44739242, 536870911, 178956970, 2147483647, 715827882, 8589934591, 2863311530

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

From Colin Barker, Feb 22 2017: (Start)

Conjectures:

a(n) = 2^(n+1) - 1 for n>1 and even.

a(n) = (2^n - 2) / 3 for n>1 and odd.

a(n) = 5*a(n-2) - 4*a(n-4) for n>3.

G.f.: (1 + 2*x + 2*x^2 - 8*x^3 + 8*x^5) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 + 2*x)).

(End)

Mathematica

CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code = 507; 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. A282800, A282801, A282802.

Sequence in context: A176379 A282454 A282655 * A341093 A248683 A110987

Adjacent sequences: A282800 A282801 A282802 * A282804 A282805 A282806

Keyword

nonn,easy

Author

Robert Price, Feb 21 2017

Status

approved