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A363669
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a(n) = Sum_{d|n} (n/d)^n * binomial(d+n-1,d).
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1
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1, 11, 91, 1219, 15751, 299291, 5766517, 136667939, 3490056406, 100539251801, 3138428729437, 107169878769043, 3937376390899589, 155639310270607349, 6568429274592664981, 295186202455912472867, 14063084452068891794119, 708261127356256620907496
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = [x^n] Sum_{k>0} (1/(1 - (k*x)^k)^n - 1).
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MATHEMATICA
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a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + n - 1, #] &]; Array[a, 20] (* Amiram Eldar, Jul 12 2023 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, (n/d)^n*binomial(d+n-1, d));
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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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