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 A338661 #19 Aug 04 2025 05:13:17
%S A338661 1,5,28,289,3126,49036,823544,17040385,387538588,10048833246,
%T A338661 285311670612,8929334253419,302875106592254,11116754387182648,
%U A338661 437894348359764856,18448995959423107073,827240261886336764178,39347761059781438793815,1978419655660313589123980
%N A338661 a(n) = Sum_{d|n} d^n * binomial(d+n/d-2, d-1).
%H A338661 Seiichi Manyama, <a href="/A338661/b338661.txt">Table of n, a(n) for n = 1..386</a>
%F A338661 G.f.: Sum_{k >= 1} (k * x/(1 - (k * x)^k))^k.
%F A338661 If p is prime, a(p) = 1 + p^p.
%F A338661 a(n) ~ n^n. - _Vaclav Kotesovec_, Aug 04 2025
%t A338661 a[n_] := DivisorSum[n, #^n * Binomial[# + n/# - 2, #-1] &]; Array[a, 20] (* _Amiram Eldar_, Apr 22 2021 *)
%o A338661 (PARI) a(n) = sumdiv(n, d, d^n*binomial(d+n/d-2, d-1));
%o A338661 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, (k*x/(1-(k*x)^k))^k))
%Y A338661 Cf. A023887, A157019, A157020, A324158, A324159, A339481, A339482, A339712, A343573.
%K A338661 nonn
%O A338661 1,2
%A A338661 _Seiichi Manyama_, Apr 22 2021