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

Terms

a(0) =0a(1) =0a(2) =4a(3) =24a(4) =144a(5) =960a(6) =7200a(7) =60480a(8) =564480a(9) =5806080a(10) =65318400a(11) =798336000a(12) =10538035200a(13) =149448499200