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A343548
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a(n) = Sum_{d|n} binomial(d+n-1,n).
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7
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1, 4, 11, 41, 127, 498, 1717, 6610, 24366, 93391, 352717, 1358826, 5200301, 20097076, 77562773, 300786339, 1166803111, 4539163784, 17672631901, 68933291834, 269129233484, 1052113994124, 4116715363801, 16124221819056, 63205303242628, 247961973949228, 973469736360283
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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>=1} x^k/(1 - x^k)^(n+1).
a(n) = [x^n] Sum_{k>=1} binomial(k+n-1,n) * x^k/(1 - x^k).
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MATHEMATICA
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a[n_] := DivisorSum[n, Binomial[# + n - 1, n] &]; Array[a, 30] (* Amiram Eldar, Apr 25 2021 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, binomial(d+n-1, 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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