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 A272220 First differences of number of active (ON,black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 438", based on the 5-celled von Neumann neighborhood. 1
 4, 3, 12, 12, 8, -4, 64, 13, -1, 28, 52, 32, 20, 12, 96, 28, 60, 32, 56, 12, 12, 36, 112, 16, 160, 36, 204, -68, 4, 24, 372, -15, 127, -60, 353, -17, 88, -116, 324, 52, 212, -172, 280, 252, -64, 41, 499, -351, 283, 121, 343, 145, -133, -103, 615, 73, 7, 109 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 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..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=438; 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. A272217. Sequence in context: A323931 A205371 A270633 * A231427 A215942 A054908 Adjacent sequences:  A272217 A272218 A272219 * A272221 A272222 A272223 KEYWORD sign,easy AUTHOR Robert Price, Apr 22 2016 STATUS approved

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Last modified March 30 08:26 EDT 2020. Contains 333119 sequences. (Running on oeis4.)