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A368890
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a(n) = Sum_{k=0..floor(n/2)} n^(3*(n-2*k)) * binomial(n-k,k).
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0
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1, 1, 65, 19737, 16789505, 30525391000, 101570840860033, 558574349855881107, 4722492584690006360065, 58150612359276833311664895, 1000009000028000035000015000001, 23225285520096132372224712190010064, 708804486128121003209727133170234347521
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = [x^n] 1/(1 - n^3*x - x^2).
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MATHEMATICA
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Join[{1}, Table[n^(3*n) * Hypergeometric2F1[1/2 - n/2, -n/2, -n, -4/n^6], {n, 1, 15}]] (* Vaclav Kotesovec, Jan 09 2024 *)
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PROG
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(PARI) a(n) = sum(k=0, n\2, n^(3*(n-2*k))*binomial(n-k, k));
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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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