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A288834
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a(n) = (n+1) * 3^(n-1).
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7
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2, 9, 36, 135, 486, 1701, 5832, 19683, 65610, 216513, 708588, 2302911, 7440174, 23914845, 76527504, 243931419, 774840978, 2453663097, 7748409780, 24407490807, 76709256822, 240588123669, 753145430616, 2353579470675, 7343167948506, 22876792454961
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OFFSET
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1,1
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LINKS
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FORMULA
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O.g.f.: z*(2-3*z)/(1-3*z)^2.
Sum_{n>=1} 1/a(n) = 9*log(3/2) - 3.
Sum_{n>=1} (-1)^(n+1)/a(n) = 3 - 9*log(4/3). (End)
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MATHEMATICA
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LinearRecurrence[{6, -9}, {2, 9}, 40] (* Harvey P. Dale, Dec 16 2018 *)
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PROG
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(PARI) Vec((z*(2-3*z)/(1-3*z)^2) + O(z^30)) \\ Felix Fröhlich, Jun 19 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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