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 A306630 #9 Mar 05 2019 01:53:40
%S A306630 1,-1,-3,-201,-328975,-24866803361,-139308071489312831,
%T A306630 -82606210548424879390169217,-6984963414431972003347406551951687935,
%U A306630 -109110687852301656115645192848607902864427297823233
%N A306630 a(n) = [x^n] 1/(Sum_{k=0..n} (k!)^n * x^k).
%H A306630 Seiichi Manyama, <a href="/A306630/b306630.txt">Table of n, a(n) for n = 0..30</a>
%Y A306630 Main diagonal of A306629.
%K A306630 sign
%O A306630 0,3
%A A306630 _Seiichi Manyama_, Mar 02 2019