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A246461
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a(n) = Sum_{k=0..n} ((2k+1)*C(n,k)*C(n+k,k))^2, where C(n,k) denotes the binomial coefficient n!/(k!*(n-k)!).
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4
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1, 37, 1225, 43397, 1563401, 56309885, 2020496185, 72190600165, 2569004841385, 91095128385485, 3220006254279233, 113505318773615741, 3991330807880182105, 140050346341652428141, 4904787249549605102233, 171480516047539645266725
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OFFSET
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0,2
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COMMENTS
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Zhi-Wei Sun noted that for any positive integer n we have Sum_{k=0..n-1} (2k+1)*a(k) = n^4*A246460(n).
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LINKS
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FORMULA
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Recurrence: n^3*(2*n-3)*(4*n^4 - 24*n^3 + 50*n^2 - 42*n + 11)*(6*n^4 - 36*n^3 + 67*n^2 - 39*n - 4)*a(n) = (2*n-1)*(840*n^11 - 10464*n^10 + 53192*n^9 - 137864*n^8 + 172296*n^7 - 19912*n^6 - 226019*n^5 + 271559*n^4 - 92324*n^3 - 42188*n^2 + 39128*n - 8466)*a(n-1) - (2*n-3)*(840*n^11 - 8016*n^10 + 28712*n^9 - 44872*n^8 + 15880*n^7 + 43992*n^6 - 64675*n^5 + 32567*n^4 + 1692*n^3 - 9364*n^2 + 4072*n - 606)*a(n-2) + (n-2)^3*(2*n-1)*(4*n^4 - 8*n^3 + 2*n^2 + 2*n - 1)*(6*n^4 - 12*n^3 - 5*n^2 + 11*n - 6)*a(n-3). - Vaclav Kotesovec, Aug 27 2014
a(n) ~ sqrt(24+17*sqrt(2)) * (17+12*sqrt(2))^n * sqrt(n) / (2*sqrt(2)*Pi^(3/2)). - Vaclav Kotesovec, Aug 27 2014
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EXAMPLE
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a(1) = 37 since Sum_{k=0..1} ((2k+1)*C(1,k)*C(1+k,k))^2 = 1^2 + (3*2)^2 = 37.
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MAPLE
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MATHEMATICA
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a[n_]:=Sum[((2k+1)*Binomial[n, k]*Binomial[n+k, k])^2, {k, 0, n}]
Table[a[n], {n, 0, 15}]
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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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