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 A273790 Partial sums of the number of active (ON,black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 931", based on the 5-celled von Neumann neighborhood. 1
 1, 6, 31, 80, 161, 282, 451, 676, 965, 1326, 1767, 2296, 2921, 3650, 4491, 5452, 6541, 7766, 9135, 10656, 12337, 14186, 16211, 18420, 20821, 23422, 26231, 29256, 32505, 35986, 39707, 43676, 47901, 52390, 57151, 62192, 67521, 73146, 79075, 85316, 91877, 98766 (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 31 2016: (Start) a(n) = (4*n^3+12*n^2+11*n-9)/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+2*x+13*x^2-12*x^3+4*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=931; 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. A273789. Sequence in context: A215730 A187508 A087725 * A096959 A112562 A244716 Adjacent sequences:  A273787 A273788 A273789 * A273791 A273792 A273793 KEYWORD nonn,easy AUTHOR Robert Price, May 30 2016 STATUS approved

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Last modified February 27 19:23 EST 2020. Contains 332308 sequences. (Running on oeis4.)