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 A349891 #12 Dec 10 2021 02:28:12
%S A349891 1,0,16,19619,4294436111,298022124379673232,
%T A349891 10314423867168242405282727694,
%U A349891 256923577039829077600620024397823949901879,6277101735175093150055816289268196664555481440709896684157
%N A349891 a(n) = Sum_{k=0..n} (-1)^(n-k) * k^(k*n).
%F A349891 G.f.: Sum_{k>=0} k^(k^2) * x^k/(1 + k^k * x).
%F A349891 a(n) ~ n^(n^2). - _Vaclav Kotesovec_, Dec 10 2021
%o A349891 (PARI) a(n) = sum(k=0, n, (-1)^(n-k)*k^(k*n));
%o A349891 (PARI) my(N=10, x='x+O('x^N)); Vec(sum(k=0, N, k^k^2*x^k/(1+k^k*x)))
%Y A349891 Cf. A120485, A349886, A349889.
%K A349891 nonn
%O A349891 0,3
%A A349891 _Seiichi Manyama_, Dec 04 2021