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 A269711 Number of active (ON,black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 20", based on the 5-celled von Neumann neighborhood. 4
 1, 4, 8, 12, 20, 24, 44, 28, 52, 56, 104, 56, 104, 112, 212, 60, 116, 120, 232, 120, 232, 240, 464, 120, 232, 240, 464, 240, 464, 480, 932, 124, 244, 248, 488, 248, 488, 496, 976, 248, 488, 496, 976, 496, 976, 992, 1952, 248, 488, 496, 976, 496, 976, 992 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Initialized with a single black (ON) cell at stage zero. Rules 28, 52, 60, 148, 156, 180, 188, 532, 540, 564, 572, 660, 668, 692 and 700 also generate this sequence. Apparently a duplicate of A122108. - R. J. Mathar, Mar 09 2016 REFERENCES S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170. LINKS Robert Price, Table of n, a(n) for n = 0..300 Robert Price, Diagrams of first 20 stages. 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 rule=20; 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 *) Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *) CROSSREFS Sequence in context: A033691 A090658 A268799 * A122108 A311658 A311659 Adjacent sequences:  A269708 A269709 A269710 * A269712 A269713 A269714 KEYWORD nonn,easy AUTHOR Robert Price, Mar 04 2016 STATUS approved

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Last modified April 19 02:19 EDT 2021. Contains 343105 sequences. (Running on oeis4.)