a(n) = (2n)!(2n+1)!/n!^4, or equally (2n+1)*binomial(2n,n)^2.

A000515

a(n) = (2n)!(2n+1)!/n!^4, or equally (2n+1)*binomial(2n,n)^2.

Terms

    a(0) =1a(1) =12a(2) =180a(3) =2800a(4) =44100a(5) =698544a(6) =11099088a(7) =176679360a(8) =2815827300a(9) =44914183600a(10) =716830370256

External references