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 A370247 #8 Feb 13 2024 07:43:13
%S A370247 1,2,10,59,362,2277,14575,94474,618154,4074197,27008885,179897720,
%T A370247 1202961215,8070830588,54302131642,366252974259,2475575739306,
%U A370247 16764524795037,113719280941453,772551326290528,5255393538550837,35794109754866998,244060675562790316
%N A370247 Coefficient of x^n in the expansion of ( 1/(1-x)^2 * (1+x^3) )^n.
%F A370247 a(n) = Sum_{k=0..floor(n/3)} binomial(n,k) * binomial(3*n-3*k-1,n-3*k).
%F A370247 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 A369265.
%o A370247 (PARI) a(n, s=3, t=1, u=2) = sum(k=0, n\s, binomial(t*n, k)*binomial((u+1)*n-s*k-1, n-s*k));
%Y A370247 Cf. A369265, A370213.
%K A370247 nonn
%O A370247 0,2
%A A370247 _Seiichi Manyama_, Feb 13 2024