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 A385840 #16 Jul 12 2025 21:33:31
%S A385840 1,1,2,10,101,1733,45303,1680907,84166419,5475072843,449157456364,
%T A385840 45377436182152,5537042709272831,802969519178558759,
%U A385840 136516626968319610486,26895468447194766859402,6078661245454015521843883,1562271796018872884111521763,453071380100390505646644605866
%N A385840 a(n) = 1 + Sum_{k=0..n-1} k^2 * a(k) * a(n-1-k).
%H A385840 Seiichi Manyama, <a href="/A385840/b385840.txt">Table of n, a(n) for n = 0..253</a>
%F A385840 G.f. A(x) satisfies A(x) = 1/( (1 - x) * ( 1 - x^2 * (d/dx A(x)) - x^3 * (d^2/dx^2 A(x)) ) ).
%o A385840 (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+sum(j=0, i-1, j^2*v[j+1]*v[i-j])); v;
%Y A385840 Cf. A143917, A385841, A385842, A385843.
%Y A385840 Cf. A385830, A385835, A385874.
%K A385840 nonn
%O A385840 0,3
%A A385840 _Seiichi Manyama_, Jul 09 2025