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 A277560 Binary representation of the x-axis, from the left edge to the origin, or from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 7", based on the 5-celled von Neumann neighborhood. 3
 1, 11, 0, 1111, 0, 111111, 0, 11111111, 0, 1111111111, 0, 111111111111, 0, 11111111111111, 0, 1111111111111111, 0, 111111111111111111, 0, 11111111111111111111, 0, 1111111111111111111111, 0, 111111111111111111111111, 0, 11111111111111111111111111, 0 (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 the 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 FORMULA Conjectures from Colin Barker, Nov 06 2016: (Start) G.f.: (1 + 11*x - 101*x^2 + 100*x^4)/((1 - x)*(1 + x)*(1 - 10*x)*(1 + 10*x)). a(n) = 101*a(n-2) - 100*a(n-4) for n>4. a(n) = (-1)*(-1 + (-1)^n)*(-1 - 10^n)/18 for n>0. (End) MATHEMATICA CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}]; code=7; 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. A277936. Sequence in context: A075361 A287630 A073864 * A073865 A036931 A165399 Adjacent sequences:  A277557 A277558 A277559 * A277561 A277562 A277563 KEYWORD nonn,easy AUTHOR Robert Price, Nov 05 2016 STATUS approved

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Last modified April 3 20:29 EDT 2020. Contains 333199 sequences. (Running on oeis4.)