A091137(n)/(n+1).

Terms

a(0) =1a(1) =1a(2) =4a(3) =6a(4) =144a(5) =240a(6) =8640a(7) =15120a(8) =403200a(9) =725760a(10) =43545600a(11) =79833600a(12) =201180672000a(13) =373621248000