G.f.: Sum_{n>=0} ( (1+x)^n + (1+2*x)^n )^n / 3^(n+1).

A301312

G.f.: Sum_{n>=0} ( (1+x)^n + (1+2*x)^n )^n / 3^(n+1).

Terms

    a(0) =1a(1) =15a(2) =818a(3) =75237a(4) =9704172a(5) =1610219061a(6) =326647152627

External references