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 A350308 #14 Dec 24 2021 11:04:12
%S A350308 1,1,13,2431,10027503,1107781071903,3893880730064443963,
%T A350308 506016205547402043327062969,2774765502272595019563619139799271431,
%U A350308 722310089115924894687149792741562790592722949523
%N A350308 a(n) is the constant term in the expansion of Product_{j=1..n} (Sum_{k=-j..j} x^k)^j.
%t A350308 a[n_] := Coefficient[Series[Product[Sum[x^k, {k, -j, j}]^j, {j, 1, n}], {x, 0, 0}], x, 0]; Array[a, 10, 0] (* _Amiram Eldar_, Dec 24 2021 *)
%o A350308 (PARI) a(n) = polcoef(prod(j=1, n, sum(k=-j, j, x^k)^j), 0);
%Y A350308 Cf. A350283, A350306, A350307.
%K A350308 nonn
%O A350308 0,3
%A A350308 _Seiichi Manyama_, Dec 23 2021