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 A371755 #9 Apr 05 2024 13:06:13
%S A371755 1,4,28,221,1834,15657,136137,1199014,10661184,95493145,860339723,
%T A371755 7788028028,70777321331,645359630071,5901209474518,54093485799726,
%U A371755 496910913391428,4573312196055502,42160889572810597,389258294230352460,3598732127428879981
%N A371755 a(n) = Sum_{k=0..floor(n/3)} binomial(4*n-2*k,n-3*k).
%F A371755 a(n) = [x^n] 1/((1-x-x^3) * (1-x)^(3*n)).
%F A371755 a(n) ~ 2^(8*n + 9/2) / (47 * sqrt(Pi*n) * 3^(3*n - 1/2)). - _Vaclav Kotesovec_, Apr 05 2024
%o A371755 (PARI) a(n) = sum(k=0, n\3, binomial(4*n-2*k, n-3*k));
%Y A371755 Cf. A144904, A371754, A371756.
%K A371755 nonn
%O A371755 0,2
%A A371755 _Seiichi Manyama_, Apr 05 2024