a(n) = 2*(2*n)!/n!.

A151817

a(n) = 2*(2*n)!/n!.

Terms

    a(0) =2a(1) =4a(2) =24a(3) =240a(4) =3360a(5) =60480a(6) =1330560a(7) =34594560a(8) =1037836800a(9) =35286451200

External references