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A246030
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a(n) = (5*2^(2*n)+(-2)^(n+1))/3.
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3
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1, 8, 24, 112, 416, 1728, 6784, 27392, 109056, 437248, 1746944, 6991872, 27959296, 111853568, 447381504, 1789591552, 7158235136, 28633202688, 114532286464, 458130194432, 1832518680576, 7330078916608, 29320307277824, 117281245888512, 469124949999616, 1876499867107328, 7505999334211584
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OFFSET
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0,2
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COMMENTS
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LINKS
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N. J. A. Sloane, On the No. of ON Cells in Cellular Automata, Video of talk in Doron Zeilberger's Experimental Math Seminar at Rutgers University, Feb. 05 2015: Part 1, Part 2
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FORMULA
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a(0)=1, a(1)=8; thereafter a(n)=2*a(n-1)+8*a(n-2).
G.f.: (1+6*x)/(1-2*x-8*x^2).
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MATHEMATICA
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CoefficientList[Series[(1 + 6 x) / (1 - 2 x - 8 x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 20 2015 *)
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PROG
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(Magma) I:=[1, 8]; [n le 2 select I[n] else 2*Self(n-1)+8*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Feb 20 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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