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 A283506 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 641", based on the 5-celled von Neumann neighborhood. 5
 1, 0, 5, 12, 29, 60, 125, 252, 509, 1020, 2045, 4092, 8189, 16380, 32765, 65532, 131069, 262140, 524285, 1048572, 2097149, 4194300, 8388605, 16777212, 33554429, 67108860, 134217725, 268435452, 536870909, 1073741820, 2147483645, 4294967292, 8589934589 (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 FORMULA Conjectures from Colin Barker, Mar 10 2017: (Start) G.f.: (1 - 2*x + 4*x^2 + 4*x^3) / ((1 - x)*(1 + x)*(1 - 2*x)). a(n) = 2^(n+1) - 3 for n>0 and even. a(n) = 2^(n+1) - 4 for n odd. a(n) = 2*a(n-1) + a(n-2) - 2*a(n-3) for n>3. (End) MATHEMATICA CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}]; code = 641; 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. A283504, A283505, A283507. Sequence in context: A055245 A196410 A000465 * A266471 A069306 A277088 Adjacent sequences:  A283503 A283504 A283505 * A283507 A283508 A283509 KEYWORD nonn,easy AUTHOR Robert Price, Mar 09 2017 STATUS approved

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Last modified October 23 22:04 EDT 2018. Contains 316541 sequences. (Running on oeis4.)