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A279501 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 161", based on the 5-celled von Neumann neighborhood. 4
1, 0, 5, 0, 29, 0, 93, 0, 381, 0, 1373, 0, 5501, 0, 21853, 0, 87421, 0, 349533, 0, 1398141, 0, 5592413, 0, 22369661, 0, 89478493, 0, 357913981, 0, 1431655773, 0, 5726623101, 0, 22906492253, 0, 91625969021, 0, 366503875933, 0, 1466015503741, 0, 5864062014813 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

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, Dec 14 2016: (Start)

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

G.f.: (1 + x^2 + 8*x^4 - 24*x^6 - 128*x^10) / ((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 = 161; 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. A279498, A279499, A279500.

Sequence in context: A167362 A070611 A047769 * A279548 A279701 A279604

Adjacent sequences:  A279498 A279499 A279500 * A279502 A279503 A279504

KEYWORD

nonn,easy

AUTHOR

Robert Price, Dec 13 2016

STATUS

approved

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Last modified August 6 10:01 EDT 2020. Contains 336245 sequences. (Running on oeis4.)