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%I #11 May 06 2024 18:45:52
%S 1,11,101,1011,10101,101011,1010101,10101011,101010101,1010101011,
%T 10101010101,101110101011,1011101010101,10110010101011,
%U 101111101010101,1011110110101011,10111110101010101,101111111010101011,1011111110101010101,10111111101110101011
%N Binary representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 998", based on the 5-celled von Neumann neighborhood.
%C Initialized with a single black (ON) cell at stage zero.
%D S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
%H Robert Price, <a href="/A284545/b284545.txt">Table of n, a(n) for n = 0..126</a>
%H Robert Price, <a href="/A284545/a284545.tmp.txt">Diagrams of first 20 stages</a>
%H N. J. A. Sloane, <a href="http://arxiv.org/abs/1503.01168">On the Number of ON Cells in Cellular Automata</a>, arXiv:1503.01168 [math.CO], 2015
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H Wolfram Research, <a href="http://atlas.wolfram.com/">Wolfram Atlas of Simple Programs</a>
%H <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H <a href="https://oeis.org/wiki/Index_to_2D_5-Neighbor_Cellular_Automata">Index to 2D 5-Neighbor Cellular Automata</a>
%H <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%F Conjectures from _Chai Wah Wu_, May 06 2024: (Start)
%F a(n) = 10*a(n-1) + a(n-8) - 10*a(n-9) for n > 25.
%F G.f.: (90000000000*x^25 + 81000000000*x^24 - 8000000000*x^23 + 9988900000000*x^22 - 897900000000*x^21 + 89900000000*x^20 + 10000000000*x^17 + 9000000000*x^16 - 900000000*x^15 + 11000000000*x^14 - 1000000000*x^13 + 100000000*x^11 - 10*x^8 + x^7 - 9*x^6 + x^5 - 9*x^4 + x^3 - 9*x^2 + x + 1)/(10*x^9 - x^8 - 10*x + 1). (End)
%t CAStep[rule_, a_] := Map[rule[[10 - #]] &, ListConvolve[{{0, 2, 0},{2, 1, 2}, {0, 2, 0}}, a, 2],{2}];
%t code = 998; stages = 128;
%t rule = IntegerDigits[code, 2, 10];
%t g = 2 * stages + 1; (* Maximum size of grid *)
%t a = PadLeft[{{1}}, {g, g}, 0,Floor[{g, g}/2]]; (* Initial ON cell on grid *)
%t ca = a;
%t ca = Table[ca = CAStep[rule, ca], {n, 1, stages + 1}];
%t PrependTo[ca, a];
%t (* Trim full grid to reflect growth by one cell at each stage *)
%t k = (Length[ca[[1]]] + 1)/2;
%t ca = Table[Table[Part[ca[[n]] [[j]],Range[k + 1 - n, k - 1 + n]], {j, k + 1 - n, k - 1 + n}], {n, 1, k}];
%t Table[FromDigits[Part[ca[[i]] [[i]], Range[i, 2 * i - 1]], 10], {i, 1, stages - 1}]
%Y Cf. A284544, A284546, A284547.
%K nonn,easy
%O 0,2
%A _Robert Price_, Mar 28 2017
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