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 A290660 Binary representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 899", based on the 5-celled von Neumann neighborhood. 4
 1, 11, 101, 1111, 11101, 111111, 1111101, 11111111, 111111101, 1111111111, 11111111101, 111111111111, 1111111111101, 11111111111111, 111111111111101, 1111111111111111, 11111111111111101, 111111111111111111, 1111111111111111101, 11111111111111111111 (list; graph; refs; listen; history; text; internal format)
 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 FORMULA Conjectures from Chai Wah Wu, Aug 03 2020: (Start) a(n) = 10*a(n-1) + a(n-2) - 10*a(n-3) for n > 3. G.f.: (100*x^3 - 10*x^2 + x + 1)/((x - 1)*(x + 1)*(10*x - 1)). (End) MATHEMATICA CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}]; code = 899; 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. A166956, A290661, A290662. Sequence in context: A284408 A265427 A284480 * A292688 A286519 A088292 Adjacent sequences:  A290657 A290658 A290659 * A290661 A290662 A290663 KEYWORD nonn,easy,changed AUTHOR Robert Price, Aug 08 2017 STATUS approved

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Last modified August 10 01:31 EDT 2020. Contains 336361 sequences. (Running on oeis4.)