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 A269696 Number of active (ON,black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 6", based on the 5-celled von Neumann neighborhood. 1
 1, 5, 20, 80, 320, 1280, 5120, 20480, 81920, 327680, 1310720, 5242880, 20971520, 83886080, 335544320, 1342177280 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Initialized with a single black (ON) cell at stage zero. Rules 38, 70, 102, 134, 166, 198 and 230 also generate this sequence. Apparently a duplicate of A003947. - R. J. Mathar, Mar 09 2016 REFERENCES S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170. LINKS 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, Mar 08 2016: (Start) a(n) = 5*4^(n-1) for n>0. a(n) = 4*a(n-1) for n>1. G.f.: (1+x) / (1-4*x). (End) MATHEMATICA rule=6; stages=300; ca=CellularAutomaton[{rule, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, stages]; (* Start with single black cell *) on=Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *) Part[on, 2^Range[0, Log[2, stages]]] (* Extract relevant terms *) CROSSREFS Cf. A269695. Sequence in context: A166859 A167106 A167650 * A167896 A168682 A168730 Adjacent sequences:  A269693 A269694 A269695 * A269697 A269698 A269699 KEYWORD nonn,easy AUTHOR Robert Price, Mar 03 2016 EXTENSIONS a(9)-a(15) from Lars Blomberg, Apr 12 2016 STATUS approved

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Last modified May 21 00:41 EDT 2019. Contains 323427 sequences. (Running on oeis4.)