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A340971
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a(n) = Sum_{k=0..n} n^k * binomial(n,k) * binomial(2*k,k).
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3
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1, 3, 33, 721, 23649, 1032801, 56317969, 3682424775, 280767441537, 24456613613401, 2395993939827201, 260764460901476643, 31213273328323059169, 4075382667781540713807, 576394007453263029232497
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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) = [x^n] 1/sqrt((1-x)*(1-(4*n+1)*x)).
a(n) = [x^n] (1+(2*n+1)*x+(n*x)^2)^n.
a(n) = n! * [x^n] exp((2*n+1)*x) * BesselI(0,2*n*x). - Ilya Gutkovskiy, Feb 01 2021
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MATHEMATICA
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a[0] = 1; a[n_] := Sum[n^k * Binomial[n, k] * Binomial[2*k, k], {k, 0, n}]; Array[a, 15, 0] (* Amiram Eldar, Feb 01 2021 *)
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PROG
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(PARI) {a(n) = sum(k=0, n, n^k*binomial(n, k)*binomial(2*k, k))}
(PARI) {a(n) = polcoef(1/sqrt((1-x)*(1-(4*n+1)*x)+x*O(x^n)), n)}
(PARI) {a(n) = polcoef((1+(2*n+1)*x+(n*x)^2)^n, n)}
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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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