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A172285
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a(n) = (5*2^n - 5*(-1)^n - 3*n*(-1)^n) / 9.
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3
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0, 2, 1, 6, 7, 20, 33, 74, 139, 288, 565, 1142, 2271, 4556, 9097, 18210, 36403, 72824, 145629, 291278, 582535, 1165092, 2330161, 4660346, 9320667, 18641360, 37282693, 74565414, 149130799, 298261628, 596523225, 1193046482, 2386092931, 4772185896
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = 3*a(n-2) + 2*a(n-3), n>2.
a(n+1) = 2*a(n) + (-1)^n * (2+n).
G.f.: x*(2+x)/( (1-2*x)*(1+x)^2 ).
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MAPLE
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MATHEMATICA
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Table[(5*2^n - 5*(-1)^n - 3*n*(-1)^n)/9, {n, 0, 40}] (* Wesley Ivan Hurt, Aug 27 2015 *)
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PROG
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(Magma) [(5*2^n - 5*(-1)^n - 3*n*(-1)^n) / 9: n in [0..40]]; // Vincenzo Librandi, Aug 05 2011
(PARI) first(m)=vector(m, i, i--; (5*2^i -5*(-1)^i - 3*i*(-1)^i ) / 9) \\ Anders Hellström, Aug 27 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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EXTENSIONS
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Definition replaced by explicit formula; g.f. added - R. J. Mathar, Feb 02 2010
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STATUS
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approved
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