a(n) = (4*n+1) * ( binomial(3*n,n)/(2*n+1) )^2.

A278883

a(n) = (4*n+1) * ( binomial(3*n,n)/(2*n+1) )^2.

Terms

    a(0) =1a(1) =5a(2) =81a(3) =1872a(4) =51425a(5) =1565109a(6) =50979600a(7) =1742711616a(8) =61765676577

External references