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 A365842 #13 Feb 17 2024 02:40:35
%S A365842 1,5,37,325,3141,32261,345605,3818501,43197445,497868805,5825331205,
%T A365842 69013667845,826213203973,9979713945605,121472752156677,
%U A365842 1488482728148997,18346810389299205,227319830355640325,2829629321065267205,35369618935665131525,443775430273133445125
%N A365842 Expansion of (1/x) * Series_Reversion( x*(1-x)^2/(1+x)^3 ).
%F A365842 a(n) = (1/(n+1)) * Sum_{k=0..n} binomial(2*n+k+1,k) * binomial(3*(n+1),n-k).
%F A365842 a(n) = (1/(n+1)) * [x^n] ( (1+x)^3 / (1-x)^2 )^(n+1). - _Seiichi Manyama_, Feb 17 2024
%o A365842 (PARI) a(n) = sum(k=0, n, binomial(2*n+k+1, k)*binomial(3*(n+1), n-k))/(n+1);
%Y A365842 Cf. A007297, A365843, A365844, A365845.
%K A365842 nonn
%O A365842 0,2
%A A365842 _Seiichi Manyama_, Sep 20 2023