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 A381915 #13 Mar 10 2025 09:42:57
%S A381915 1,3,18,145,1378,14515,163700,1936414,23716654,298216851,3827542585,
%T A381915 49938733635,660366743580,8830549084588,119205253249287,
%U A381915 1622258295003714,22232669093660250,306569446979862205,4250285556933578693,59210418891925845529,828417259759216617257
%N A381915 Expansion of (1/x) * Series_Reversion( x * (1-x)^2 / B(x) ), where B(x) is the g.f. of A002293.
%F A381915 G.f. A(x) satisfies A(x) = B(x*A(x)) / (1 - x*A(x))^2.
%F A381915 a(n) = Sum_{k=0..n} binomial(n+4*k+1,k) * binomial(3*n-k+1,n-k)/(n+4*k+1).
%o A381915 (PARI) a(n) = sum(k=0, n, binomial(n+4*k+1, k)*binomial(3*n-k+1, n-k)/(n+4*k+1));
%Y A381915 Cf. A381914, A381916.
%Y A381915 Cf. A381879, A381912.
%Y A381915 Cf. A002293.
%K A381915 nonn
%O A381915 0,2
%A A381915 _Seiichi Manyama_, Mar 10 2025