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 A344640 #8 May 26 2021 02:45:49
%S A344640 1,2,5,16,63,297,1649,10641,78823,662315,6241889,65294039,751035233,
%T A344640 9420926879,127958645921,1870319380463,29263787708393,487891616911031,
%U A344640 8632986776222945,161555987833199807,3187606376603319017,66128414623822131863,1438861202348688524897,32763278185929878499887
%N A344640 Antidiagonal sums of A344639.
%H A344640 Vaclav Kotesovec, <a href="/A344640/b344640.txt">Table of n, a(n) for n = 0..448</a>
%F A344640 a(n) = Sum_{k=0..n} Sum_{m=0..n-k} abs(S1(n-k, m))*(m + 1)^k, where S1 indicates the signed Stirling numbers of first kind.
%F A344640 Conjecture: a(n) ~ n!. - _Vaclav Kotesovec_, May 26 2021
%t A344640 Table[Sum[Sum[Abs[StirlingS1[n-k,m]](m+1)^k,{m,0,n-k}],{k,0,n}],{n,0,23}]
%Y A344640 Cf. A000254, A081048, A344639.
%K A344640 nonn
%O A344640 0,2
%A A344640 _Stefano Spezia_, May 25 2021