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 A374652 #12 Aug 27 2024 16:50:00
%S A374652 -1,5,5,39,181,1159,8301,67919,621941,6308679,70223101,851165119,
%T A374652 11160489861,157411458359,2376543620621,38242755444399,
%U A374652 653435591570581,11815320900966439,225408497129888541,4524816801601368479,95339744251262894501,2103888092422797642519
%N A374652 a(n) = Sum_{k=1..n+1} (-1)^(k - 1)*(k + 1)*(n - k + 1)!.
%C A374652 Residues mod 10 are 9, 5, 5, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9, 1, 9,...
%t A374652 t[n_] := Sum[(-1)^(k - 1) (k + 1)*(n - k + 1)!, {k, 1, n + 1}]
%t A374652 Table[t[n], {n, 1, 30}]
%Y A374652 Cf. A374651, A374653.
%K A374652 sign
%O A374652 1,2
%A A374652 _Clark Kimberling_, Jul 25 2024
%E A374652 Definition corrected by _Georg Fischer_, Aug 27 2024