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 A371776 #9 May 13 2025 12:20:17
%S A371776 1,6,55,561,6005,66080,740342,8400074,96206994,1109874635,12877808194,
%T A371776 150122945518,1756887201266,20628519611407,242891806678851,
%U A371776 2866906127955287,33910670558191711,401857349039547372,4770115555036932777,56706219260783415643
%N A371776 a(n) = Sum_{k=0..floor(n/3)} binomial(5*n-k+1,n-3*k).
%F A371776 a(n) = [x^n] 1/(((1-x)^2-x^3) * (1-x)^(4*n)).
%t A371776 Table[Sum[Binomial[5n-k+1,n-3k],{k,0,Floor[n/3]}],{n,0,20}] (* _Harvey P. Dale_, May 13 2025 *)
%o A371776 (PARI) a(n) = sum(k=0, n\3, binomial(5*n-k+1, n-3*k));
%Y A371776 Cf. A371773, A371774, A371775.
%K A371776 nonn
%O A371776 0,2
%A A371776 _Seiichi Manyama_, Apr 05 2024