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A345368
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a(n) = Sum_{k=0..n} binomial(5*k,k) / (4*k + 1).
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7
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1, 2, 7, 42, 327, 2857, 26608, 258488, 2588933, 26539288, 277082658, 2936050788, 31494394563, 341325970323, 3731742758203, 41108999917483, 455850863463768, 5084213586320193, 56997201842602368, 641906808539396253, 7258985455500009623, 82393287049581399283
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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G.f. A(x) satisfies: A(x) = 1 / (1 - x) + x * (1 - x)^4 * A(x)^5.
a(n) ~ 5^(5*n + 11/2) / (2869 * sqrt(Pi) * n^(3/2) * 2^(8*n + 7/2)). - Vaclav Kotesovec, Jul 28 2021
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MATHEMATICA
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Table[Sum[Binomial[5 k, k]/(4 k + 1), {k, 0, n}], {n, 0, 21}]
nmax = 21; A[_] = 0; Do[A[x_] = 1/(1 - x) + x (1 - x)^4 A[x]^5 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
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PROG
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(PARI) a(n) = sum(k=0, n, binomial(5*k, k)/(4*k+1)); \\ Michel Marcus, Jul 28 2021
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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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