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 A370283 #7 Feb 14 2024 10:48:08
%S A370283 1,3,23,201,1855,17643,171059,1680822,16679031,166763190,1677365833,
%T A370283 16953705860,172047413395,1751870166998,17890003430490,
%U A370283 183148065506136,1879053717936423,19315569214866495,198890064249729314,2051053032020625350,21180292180328586305
%N A370283 Coefficient of x^n in the expansion of 1/( (1-x)^3 - x^2 )^n.
%H A370283 a(n) = Sum_{k=0..floor(n/2)} binomial(n+k-1,k) * binomial(4*n+k-1,n-2*k).
%H A370283 The g.f. exp( Sum_{k>=1} a(k) * x^k/k ) has integer coefficients and equals (1/x) * Series_Reversion( x * ((1-x)^3 - x^2) ). See A369694.
%o A370283 (PARI) a(n) = sum(k=0, n\2, binomial(n+k-1, k)*binomial(4*n+k-1, n-2*k));
%Y A370283 Cf. A370282, A370284.
%Y A370283 Cf. A369694.
%K A370283 nonn
%O A370283 0,2
%A A370283 _Seiichi Manyama_, Feb 13 2024