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 A366557 #12 Oct 14 2023 14:00:07
%S A366557 1,1,0,1,4,6,8,29,84,162,360,1074,2808,6444,16464,45629,118244,297450,
%T A366557 790184,2138438,5624136,14778068,39767024,107287122,286593800,
%U A366557 768920084,2083170960,5642886852,15250029552,41369986008,112681853344,306930498205,836259756612
%N A366557 G.f. A(x) satisfies A(x) = 1 + x + x^3*A(x)^4.
%F A366557 a(n) = Sum_{k=0..floor(n/3)} binomial(3*k+1,n-3*k) * binomial(4*k,k)/(3*k+1).
%F A366557 a(n) = A366594(n) + A366594(n-1).
%o A366557 (PARI) a(n) = sum(k=0, n\3, binomial(3*k+1, n-3*k)*binomial(4*k, k)/(3*k+1));
%Y A366557 Cf. A137954, A366267, A366558.
%Y A366557 Cf. A366594.
%K A366557 nonn
%O A366557 0,5
%A A366557 _Seiichi Manyama_, Oct 13 2023