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 A318794 #16 Mar 17 2024 05:15:21
%S A318794 1,-10,11628,-166821980,11017028561336,-2177623431995581080,
%T A318794 1017073493827776256367100,-964251586210215914665050724728,
%U A318794 1668594120314854076064862598821148400,-4872196290698367813554985402532435243198848
%N A318794 Constant term in the expansion of (Sum_{k=0..2*n} k*(x^k - x^(-k)))^(2*n).
%F A318794 a(n) ~ (-1)^n * c * d^n * n^(4*n - 3/2), where d = 12.176292973966848533089025... and c = 1.04502891160415810516533... - _Vaclav Kotesovec_, Dec 15 2018
%t A318794 a[n_] := If[n==0, 1, Coefficient[Expand[Sum[k * (x^k - x^(-k)), {k, 0, 2n}]^(2n)], x, 0]]; Array[a, 15, 0] (* _Amiram Eldar_, Dec 15 2018 *)
%t A318794 (* Calculation of constant d: *) 64*(Sin[x]/x^2 - Cos[x]/x)^2 /. FindRoot[(2 - x^2)*Tan[x] == 2*x, {x, 2}, WorkingPrecision -> 70] (* _Vaclav Kotesovec_, Mar 17 2024 *)
%o A318794 (PARI) {a(n) = polcoeff((sum(k=0, 2*n, k*(x^k-x^(-k))))^(2*n), 0, x)}
%Y A318794 Cf. A318793.
%K A318794 sign
%O A318794 0,2
%A A318794 _Seiichi Manyama_, Dec 15 2018