This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A338663 #12 Apr 22 2021 22:05:04 %S A338663 1,9,82,1073,15626,284567,5764802,134874369,3486981232,100146490520, %T A338663 3138428376722,107039261352736,3937376385699290,155587085803983069, %U A338663 6568409424129452048,295158038428838854657,14063084452067724991010,708242105301294465144506,37589973457545958193355602 %N A338663 a(n) = Sum_{d|n} (n/d)^n * binomial(d+n/d-1, d). %F A338663 G.f.: Sum_{k >= 1} (1/(1 - (k * x)^k)^k - 1). %F A338663 If p is prime, a(p) = 1 + p^(p+1). %t A338663 a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + n/# - 1, #] &]; Array[a, 20] (* _Amiram Eldar_, Apr 22 2021 *) %o A338663 (PARI) a(n) = sumdiv(n, d, (n/d)^n*binomial(d+n/d-1, d)); %o A338663 (PARI) N=20; x='x+O('x^N); Vec(sum(k=1, N, 1/(1-(k*x)^k)^k-1)) %Y A338663 Cf. A081543, A338662. %K A338663 nonn %O A338663 1,2 %A A338663 _Seiichi Manyama_, Apr 22 2021