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 A300519 #11 Mar 08 2018 04:02:07
%S A300519 1,2,7,39,321,3603,51391,884873,17770445,406673247,10431884283,
%T A300519 296262164637,9224841015745,312441152401067,11434829066996087,
%U A300519 449675059390576257,18908960744072894325,846638474386244188311,40213487658138717885907,2019543479160709325145893
%N A300519 Convolution of n! and n^n.
%F A300519 a(n) = Sum_{k=0..n} k^k * (n-k)!.
%F A300519 a(n) ~ n^n * (1 + exp(-1)/n).
%t A300519 Table[Sum[If[k == 0, 1, k^k] * (n-k)!, {k, 0, n}], {n, 0, 20}]
%Y A300519 Cf. A000142, A000312, A061711, A277506.
%Y A300519 Cf. A107713, A108953, A110467.
%K A300519 nonn
%O A300519 0,2
%A A300519 _Vaclav Kotesovec_, Mar 08 2018