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

A385667

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

Terms

    a(0) =1a(1) =10a(2) =151a(3) =2542a(4) =44983a(5) =819160a(6) =15197404a(7) =285653350a(8) =5421341311a(9) =103659081034

External references