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 A328813 #18 May 06 2021 03:16:24
%S A328813 1,1,7,115,8071,1770951,1505946121,4368457532265,49949721645153751,
%T A328813 2021436054924485283799,327902645022367779788597977,
%U A328813 191573267131797606250658812550565,453516825886934673673734108656254582801
%N A328813 Constant term in the expansion of (-1 + Product_{k=1..n} (1 + x_k) + Product_{k=1..n} (1 + 1/x_k))^n.
%H A328813 Seiichi Manyama, <a href="/A328813/b328813.txt">Table of n, a(n) for n = 0..58</a>
%F A328813 a(n) = A328747(n,n+1) = Sum_{i=0..n} (-1)^(n-i)*binomial(n,i)*Sum_{j=0..i} binomial(i,j)^(n+1).
%t A328813 a[n_] := Sum[(-1)^(n-i) * Binomial[n, i] * Sum[Binomial[i, j]^(n+1), {j, 0, i}], {i, 0, n}]; Array[a, 13, 0] (* _Amiram Eldar_, May 06 2021 *)
%o A328813 (PARI) {a(n) = sum(i=0, n, (-1)^(n-i)*binomial(n, i)*sum(j=0, i, binomial(i, j)^(n+1)))}
%Y A328813 Cf. A328747, A328812, A328814.
%K A328813 nonn
%O A328813 0,3
%A A328813 _Seiichi Manyama_, Oct 28 2019