Partial products of A063659.

Terms

a(0) =1a(1) =2a(2) =6a(3) =18a(4) =90a(5) =540a(6) =3780a(7) =22680a(8) =181440a(9) =1814400a(10) =19958400a(11) =179625600a(12) =2335132800a(13) =32691859200a(14) =490377888000