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 A370196 #8 Feb 11 2024 09:15:52
%S A370196 1,2,6,23,102,477,2259,10733,51174,245156,1180381,5709387,27723315,
%T A370196 135055845,659744973,3230479173,15850993126,77918426928,383646423564,
%U A370196 1891715752242,9340099603677,46170434726054,228479085858447,1131770152854441,5611302030239667
%N A370196 Coefficient of x^n in the expansion of ( (1+x)^2 * (1+x^3) )^n.
%F A370196 a(n) = Sum_{k=0..floor(n/3)} binomial(n,k) * binomial(2*n,n-3*k).
%F A370196 The g.f. exp( Sum_{k>=1} a(k) * x^k/k ) has integer coefficients and equals (1/x) * Series_Reversion( x / ((1+x)^2 * (1+x^3)) ). See A369443.
%o A370196 (PARI) a(n, s=3, t=1, u=2) = sum(k=0, n\s, binomial(t*n, k)*binomial(u*n, n-s*k));
%Y A370196 Cf. A369443.
%K A370196 nonn,easy
%O A370196 0,2
%A A370196 _Seiichi Manyama_, Feb 11 2024