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 A273744 Partial sums of the number of active (ON,black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 901", based on the 5-celled von Neumann neighborhood. 1
 1, 9, 34, 83, 164, 285, 454, 679, 968, 1329, 1770, 2299, 2924, 3653, 4494, 5455, 6544, 7769, 9138, 10659, 12340, 14189, 16214, 18423, 20824, 23425, 26234, 29259, 32508, 35989, 39710, 43679, 47904, 52393, 57154, 62195, 67524, 73149, 79078, 85319, 91880, 98769 (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..128 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, May 29 2016: (Start) a(n) = n*(11+12*n+4*n^2)/3 for n>0. a(n) = 4*a(n-1)-6*a(n-2)+4*a(n-3)-a(n-4) for n>4. G.f.: (1+5*x+4*x^2-3*x^3+x^4) / (1-x)^4. (End) MATHEMATICA CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}]; code=901; 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)/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}]; on=Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *) Table[Total[Part[on, Range[1, i]]], {i, 1, Length[on]}] (* Sum at each stage *) CROSSREFS Cf. A273743. Sequence in context: A262959 A139275 A236370 * A133547 A100179 A106598 Adjacent sequences:  A273741 A273742 A273743 * A273745 A273746 A273747 KEYWORD nonn,easy AUTHOR Robert Price, May 28 2016 STATUS approved

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Last modified August 23 11:24 EDT 2019. Contains 326222 sequences. (Running on oeis4.)