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 A273560 First differences of number of active (ON,black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 785", based on the 5-celled von Neumann neighborhood. 1
 3, 9, 15, 21, 28, 27, 37, 39, 61, 27, 85, 39, 93, 59, 85, 71, 125, 59, 149, 71, 157, 91, 149, 103, 173, 91, 181, 135, 157, 123, 181, 135, 253, 123, 277, 135, 285, 155, 277, 167, 301, 155, 309, 199, 285, 187, 309, 199, 365, 187, 373, 231, 341, 235, 341, 247 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Initialized with a single black (ON) cell at stage zero. First negative term is a(124) = -83. - Georg Fischer, Feb 15 2019 REFERENCES S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170. LINKS Robert Price, Table of n, a(n) for n = 0..127 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 MATHEMATICA CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}]; code=785; 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}]; on=Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *) Table[on[[i+1]]-on[[i]], {i, 1, Length[on]-1}] (* Difference at each stage *) CROSSREFS Cf. A273557. Sequence in context: A162843 A102954 A272749 * A246388 A272793 A273567 Adjacent sequences: A273557 A273558 A273559 * A273561 A273562 A273563 KEYWORD sign,easy AUTHOR Robert Price, May 25 2016 STATUS approved

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Last modified December 6 16:00 EST 2022. Contains 358644 sequences. (Running on oeis4.)