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 A273501 First differences of number of active (ON,black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 771", based on the 5-celled von Neumann neighborhood. 1
 4, 12, 16, 32, 24, 48, 24, 96, 40, 80, 24, 160, 40, 112, -8, 320, 72, 144, 24, 288, 40, 176, -72, 576, 72, 208, -40, 480, -24, 240, -264, 1152, 136, 272, 24, 544, 40, 304, -200, 1088, 72, 336, -168, 864, -152, 368, -648, 2176, 136, 400, -104, 928, -88, 432 (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=771; 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 *) Y Cf. A273499. CROSSREFS Sequence in context: A152680 A270248 A228274 * A291781 A253122 A239413 Adjacent sequences:  A273498 A273499 A273500 * A273502 A273503 A273504 KEYWORD sign,easy AUTHOR Robert Price, May 23 2016 STATUS approved

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Last modified April 9 10:32 EDT 2020. Contains 333348 sequences. (Running on oeis4.)