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 A370270 #8 Feb 14 2024 10:48:45
%S A370270 1,2,16,110,840,6502,51424,411602,3326600,27082460,221776016,
%T A370270 1824750424,15073212648,124926064460,1038330110400,8651387371360,
%U A370270 72238476287112,604327981885262,5064140053702240,42500097815152940,357157266768270840,3005093769261481238
%N A370270 Coefficient of x^n in the expansion of 1/( (1-x)^2 * (1-x^2)^3 )^n.
%F A370270 a(n) = Sum_{k=0..floor(n/2)} binomial(3*n+k-1,k) * binomial(3*n-2*k-1,n-2*k).
%F A370270 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^2)^3 ). See A365879.
%o A370270 (PARI) a(n, s=2, t=3, u=2) = sum(k=0, n\s, binomial(t*n+k-1, k)*binomial((u+1)*n-s*k-1, n-s*k));
%Y A370270 Cf. A365879.
%K A370270 nonn
%O A370270 0,2
%A A370270 _Seiichi Manyama_, Feb 13 2024