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 A336247 #15 May 03 2021 12:16:10
%S A336247 1,2,9,460,684545,50547203126,280807908057046657,
%T A336247 165858480204085842350156792,13997217669604247492958380810030809089,
%U A336247 218434494471443385260764665498960241287478619115850,792268399795067334328715213043856435592857850955707257780000000001
%N A336247 a(n) = (n!)^n * Sum_{k=0..n} 1 / (k!)^n.
%H A336247 Seiichi Manyama, <a href="/A336247/b336247.txt">Table of n, a(n) for n = 0..30</a>
%t A336247 Table[(n!)^n Sum[1/(k!)^n, {k, 0, n}], {n, 0, 10}]
%o A336247 (PARI) a(n) = (n!)^n * sum(k=0, n, 1/(k!)^n); \\ _Michel Marcus_, Jul 14 2020
%Y A336247 Cf. A000522, A006040, A036740, A060943, A217284, A336248.
%Y A336247 Main diagonal of A343863.
%K A336247 nonn
%O A336247 0,2
%A A336247 _Ilya Gutkovskiy_, Jul 14 2020