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 A365839 #9 Sep 20 2023 10:01:27
%S A365839 1,5,38,345,3454,36786,408848,4687969,55048310,658645110,8001060132,
%T A365839 98419541226,1223430822028,15344868505700,193952279202660,
%U A365839 2467977904556145,31589883835911846,406463726382152142,5254324418131556900,68206459568715464110,888731044203480723076
%N A365839 Expansion of (1/x) * Series_Reversion( x*(1-x)^3/(1+x)^2 ).
%F A365839 a(n) = (1/(n+1)) * Sum_{k=0..n} binomial(3*n+k+2,k) * binomial(2*(n+1),n-k).
%o A365839 (PARI) a(n) = sum(k=0, n, binomial(3*n+k+2, k)*binomial(2*(n+1), n-k))/(n+1);
%Y A365839 Cf. A032349, A365840, A365841.
%K A365839 nonn
%O A365839 0,2
%A A365839 _Seiichi Manyama_, Sep 20 2023