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A176812
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Expansion of 3*(1+x)/(1-2*x-5*x^2).
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1
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3, 9, 33, 111, 387, 1329, 4593, 15831, 54627, 188409, 649953, 2241951, 7733667, 26677089, 92022513, 317430471, 1094973507, 3777099369, 13029066273, 44943629391, 155032590147, 534783327249, 1844729605233, 6363375846711
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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Binet form: a(n)=2^n*(((3 + Sqrt[6])/2)*((1 + Sqrt[6])/2)^n + ((3 - Sqrt[6])/2)*((1 - Sqrt[6])/2)^n) = 3*A180168(n).
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MATHEMATICA
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a[n_] = 2^n*(((3 + Sqrt[ 6])/2)*((1 + Sqrt[6])/2)^n + ((3 - Sqrt[6])/2)*((1 - Sqrt[6])/2)^n); Table[FullSimplify[a[n]], {n, 0, 30}]
CoefficientList[Series[(-3(1+x))/(5x^2+2x-1), {x, 0, 40}], x] (* Harvey P. Dale, Feb 24 2011 *)
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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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