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 A366266 #13 Oct 10 2023 16:39:27
%S A366266 1,2,6,30,170,1050,6846,46374,323154,2301618,16680246,122607342,
%T A366266 911868282,6849381194,51885977838,395941193718,3040818657954,
%U A366266 23485437201762,182297207394150,1421357996034750,11126867651367498,87421958424703098,689130671539597854
%N A366266 G.f. A(x) satisfies A(x) = 1 + x + x*A(x)^3.
%F A366266 a(n) = Sum_{k=0..n} binomial(2*k+1,n-k) * binomial(3*k,k)/(2*k+1).
%F A366266 a(n) = A366221(n) + A366221(n-1).
%F A366266 G.f.: A(x) = 1/B(-x) where B(x) is the g.f. of A366364.
%o A366266 (PARI) a(n) = sum(k=0, n, binomial(2*k+1, n-k)*binomial(3*k, k)/(2*k+1));
%Y A366266 Cf. A025227, A366267, A366268.
%Y A366266 Cf. A366221, A366364.
%K A366266 nonn
%O A366266 0,2
%A A366266 _Seiichi Manyama_, Oct 06 2023