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 A366204 #6 Oct 08 2023 09:25:09
%S A366204 1,3,22,305,6873,223300,9609372,517122117,33450100420,2528420918595,
%T A366204 218708219876094,21304932729509468,2307805461194581390,
%U A366204 275157252809857575960,35806664475402303854328,5049845899886455033320237,767208489677203200554103660,124917404793477227061928480153
%N A366204 a(n) = (1/n) * Sum_{k=0..n-1} binomial(n+k-1,k) * binomial(4*n,n-k-1) * (n-3)^k.
%C A366204 a(n) is the coefficient of x^n in expansion of series reversion of g.f. for n-gonal pyramidal numbers (with signs).
%F A366204 a(n) = [x^n] Series_Reversion( x * (1 - (n - 3) * x) / (1 + x)^4 ).
%t A366204 Unprotect[Power]; 0^0 = 1; Table[1/n Sum[Binomial[n + k - 1, k] Binomial[4 n, n - k - 1] (n - 3)^k, {k, 0, n - 1}], {n, 1, 18}]
%t A366204 Table[Binomial[4 n, n - 1] Hypergeometric2F1[1 - n, n, 3 n + 2, 3 - n]/n, {n, 1, 18}]
%t A366204 Table[SeriesCoefficient[InverseSeries[Series[x (1 - (n - 3) x)/(1 + x)^4, {x, 0, n}], x], {x, 0, n}], {n, 1, 18}]
%Y A366204 Cf. A002293, A006484, A323208, A365754, A366014, A366015, A366016, A366017, A366203.
%K A366204 nonn
%O A366204 1,2
%A A366204 _Ilya Gutkovskiy_, Oct 04 2023