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A288761 Binary representation of the diagonal from the origin to the corner of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 501", based on the 5-celled von Neumann neighborhood. 4
1, 1, 100, 111, 11000, 11111, 1100000, 111111, 110000000, 11111111, 11000000000, 1111111111, 1100000000000, 111111111111, 110000000000000, 11111111111111, 11000000000000000, 1111111111111111, 1100000000000000000, 111111111111111111, 110000000000000000000 (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, Jun 15 2017: (Start)

G.f.: (1 + x - x^2 + 10*x^3 + 1000*x^4 - 1000*x^6 - 1000000*x^7 + 1000000*x^9) / ((1 - x)*(1 + x)*(1 - 10*x)*(1 + 10*x)).

a(n) = 11*10^(n - 1) for n>5 and even.

a(n) = (10^n - 10)/90 for n>5 and odd.

a(n) = 101*a(n-2) - 100*a(n-4) for n>4.

(End)

MATHEMATICA

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

code = 501; 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]], 10], {i, 1, stages - 1}]

CROSSREFS

Cf. A288020, A288762, A288763.

Sequence in context: A285652 A280411 A288297 * A088477 A328864 A143919

Adjacent sequences:  A288758 A288759 A288760 * A288762 A288763 A288764

KEYWORD

nonn,easy

AUTHOR

Robert Price, Jun 15 2017

STATUS

approved

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Last modified October 23 19:26 EDT 2021. Contains 348215 sequences. (Running on oeis4.)