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 A366646 #10 Oct 15 2023 09:26:05
%S A366646 1,0,0,0,1,4,10,20,39,88,228,600,1507,3652,8866,22100,56365,144656,
%T A366646 369784,942480,2408934,6196280,16026652,41571640,107959654,280708560,
%U A366646 731349400,1910098320,4999759830,13109582376,34421585844,90500370760,238272324682
%N A366646 G.f. A(x) satisfies A(x) = 1 + (x * A(x) / (1 - x))^4.
%F A366646 a(n) = Sum_{k=0..floor(n/4)} binomial(n-1,n-4*k) * binomial(4*k,k) / (3*k+1).
%o A366646 (PARI) a(n) = sum(k=0, n\4, binomial(n-1, n-4*k)*binomial(4*k, k)/(3*k+1));
%Y A366646 Partial sums give A127902.
%Y A366646 Cf. A213336, A364410, A366645.
%Y A366646 Cf. A002026, A361932.
%K A366646 nonn
%O A366646 0,6
%A A366646 _Seiichi Manyama_, Oct 15 2023