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 A354899 #14 Jun 11 2022 07:52:29
%S A354899 1,5,28,281,3126,48517,823544,16995617,387692650,10047310481,
%T A354899 285311670612,8932562801857,302875106592254,11119129387084097,
%U A354899 437899615088648176,18451106376806703617,827240261886336764178,39349894934527426209025
%N A354899 a(n) = n! * Sum_{d|n} d^d / (d! * (n/d)!).
%F A354899 E.g.f.: Sum_{k>0} k^k * (exp(x^k) - 1)/k!.
%F A354899 If p is prime, a(p) = 1 + p^p.
%t A354899 a[n_] := n! * DivisorSum[n, #^#/(#! * (n/#)!) &]; Array[a, 18] (* _Amiram Eldar_, Jun 11 2022 *)
%o A354899 (PARI) a(n) = n!*sumdiv(n, d, d^d/(d!*(n/d)!));
%o A354899 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=1, N, k^k*(exp(x^k)-1)/k!)))
%Y A354899 Cf. A121860, A354844, A354888, A354897, A354900.
%K A354899 nonn
%O A354899 1,2
%A A354899 _Seiichi Manyama_, Jun 11 2022