a(n) = 2^n*n!*(2*n+1).

Terms

a(0) =1a(1) =6a(2) =40a(3) =336a(4) =3456a(5) =42240a(6) =599040a(7) =9676800a(8) =175472640a(9) =3530096640a(10) =78033715200