a(n) = Sum_{k=0..n} 2^k * binomial(3*n,k) * binomial(3*n-k-1,n-k).

A385320

a(n) = Sum_{k=0..n} 2^k * binomial(3*n,k) * binomial(3*n-k-1,n-k).

Terms

    a(0) =1a(1) =8a(2) =118a(3) =1970a(4) =34714a(5) =630548a(6) =11678284a(7) =219240008a(8) =4157096266a(9) =79429466456

External references