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 A385876 #8 Jul 11 2025 08:49:21
%S A385876 1,1,2,12,193,6968,495189,62906143,13274340034,4393943557987,
%T A385876 2179423896462618,1560476564415661780,1563601961040080858376,
%U A385876 2135883440687340361131857,3889446901597262416621276499,9260777373178278371280728311304,28347247357191779349093896687278933
%N A385876 a(n) = 1 + Sum_{k=0..n-1} binomial(k+3,4) * a(k) * a(n-1-k).
%F A385876 G.f. A(x) satisfies A(x) = 1/( (1 - x) * ( 1 - x*Sum_{k=1..4} binomial(3,k-1) * x^k/k! * (d^k/dx^k A(x)) ) ).
%o A385876 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+sum(j=0, i-1, binomial(j+3, 4)*v[j+1]*v[i-j])); v;
%Y A385876 Cf. A143917, A385874, A385875, A385877.
%Y A385876 Cf. A385842.
%K A385876 nonn
%O A385876 0,3
%A A385876 _Seiichi Manyama_, Jul 11 2025