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 A372462 #6 May 02 2024 09:46:14
%S A372462 1,3,17,105,673,4403,29183,195170,1313889,8889963,60392717,411615867,
%T A372462 2813115487,19270525316,132273530462,909530996780,6263834506593,
%U A372462 43198661550219,298296958413785,2062180461738075,14271253423675773,98859742466265935
%N A372462 Coefficient of x^n in the expansion of 1 / ( (1-x) * (1-x+x^2)^2 )^n.
%F A372462 a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(2*n+k-1,k) * binomial(4*n-k-1,n-2*k).
%F A372462 The g.f. exp( Sum_{k>=1} a(k) * x^k/k ) has integer coefficients and equals (1/x) * Series_Reversion( x * (1-x) * (1-x+x^2)^2 ). See A368973.
%o A372462 (PARI) a(n, s=2, t=2, u=1) = sum(k=0, n\s, (-1)^k*binomial(t*n+k-1, k)*binomial((t+u+1)*n-(s-1)*k-1, n-s*k));
%Y A372462 Cf. A368973, A372458.
%K A372462 nonn
%O A372462 0,2
%A A372462 _Seiichi Manyama_, May 01 2024