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 A279118 Binary representation of the x-axis, from the left edge to the origin, (and also from the origin to the right edge) of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 209", based on the 5-celled von Neumann neighborhood. 4
 1, 0, 111, 0, 11111, 0, 1111111, 0, 111111111, 0, 11111111111, 0, 1111111111111, 0, 111111111111111, 0, 11111111111111111, 0, 1111111111111111111, 0, 111111111111111111111, 0, 11111111111111111111111, 0, 1111111111111111111111111, 0 (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 Chai Wah Wu, Aug 02 2021: (Start) a(n) = 101*a(n-2) - 100*a(n-4) for n > 3. G.f.: (10*x^2 + 1)/(100*x^4 - 101*x^2 + 1). (End) MATHEMATICA CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}]; code = 209; 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. A279872. Sequence in context: A279720 A282265 A282295 * A282411 A282674 A282678 Adjacent sequences: A279115 A279116 A279117 * A279119 A279120 A279121 KEYWORD nonn,easy AUTHOR Robert Price, Dec 21 2016 STATUS approved

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Last modified July 19 22:34 EDT 2024. Contains 374441 sequences. (Running on oeis4.)