A363662 a(n) = Sum_{d|n} (n/d)^n * binomial(d+n,n).
2, 18, 128, 1590, 19002, 353304, 6591776, 154083654, 3878583770, 110647791078, 3423740752764, 116116072618104, 4240251502692142, 166761491097360240, 7006327371058071648, 313637735782416564806, 14890324713956395361406, 747610406539465959084870
Offset: 1
Keywords
Programs
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Mathematica
a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + n, n] &]; Array[a, 20] (* Amiram Eldar, Jul 12 2023 *)
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PARI
a(n) = sumdiv(n, d, (n/d)^n*binomial(d+n, n));
Formula
a(n) = [x^n] Sum_{k>0} (1/(1 - (k*x)^k)^(n+1) - 1).