%I #7 Apr 06 2024 10:04:59

%S 1,6,55,561,6005,66080,740342,8400074,96206994,1109874635,12877808194,

%T 150122945518,1756887201266,20628519611407,242891806678851,

%U 2866906127955287,33910670558191711,401857349039547372,4770115555036932777,56706219260783415643

%N a(n) = Sum_{k=0..floor(n/3)} binomial(5*n-k+1,n-3*k).

%F a(n) = [x^n] 1/(((1-x)^2-x^3) * (1-x)^(4*n)).

%o (PARI) a(n) = sum(k=0, n\3, binomial(5*n-k+1, n-3*k));

%Y Cf. A371773, A371774, A371775.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Apr 05 2024