a(n) = numerator(n!/n^2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =24a(5) =20a(6) =720a(7) =630a(8) =4480a(9) =36288a(10) =3628800a(11) =3326400a(12) =479001600a(13) =444787200a(14) =5811886080a(15) =81729648000