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 A308327 #17 May 22 2019 21:03:35
%S A308327 1,-1,1,-120,1056496,-2063348839223,1457689055077930674637,
%T A308327 -569779896381467292745562607320194,
%U A308327 174622933743914766946635359968704455433117668396,-56466564044341292662007179162722871704054012257606338926938133618
%N A308327 a(n) = (1/n!) * Sum_{i_1=1..n} Sum_{i_2=1..n} ... Sum_{i_n=1..n} (-1)^(i_1 + i_2 + ... + i_n) * multinomial(i_1 + i_2 + ... + i_n; i_1, i_2, ..., i_n).
%H A308327 Seiichi Manyama, <a href="/A308327/b308327.txt">Table of n, a(n) for n = 0..27</a>
%e A308327 a(2) = (1/2) * (binomial(1+1,1) - binomial(1+2,2) - binomial(2+1,1) + binomial(2+2,2)) = 1.
%o A308327 (PARI) {a(n) = sum(i=n, n^2, (-1)^i*i!*polcoef(sum(j=1, n, x^j/j!)^n, i))/n!}
%Y A308327 Main diagonal of A308356.
%Y A308327 Cf. A308296.
%K A308327 sign
%O A308327 0,4
%A A308327 _Seiichi Manyama_, May 20 2019