Distinct elements of A045948.

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =24a(5) =120a(6) =360a(7) =720a(8) =5040a(9) =10080a(10) =30240a(11) =332640a(12) =1663200a(13) =3326400a(14) =43243200a(15) =129729600a(16) =259459200a(17) =4410806400a(18) =30875644800a(19) =586637251200