a(n) = n! / (floor(n/3))! - n! / (floor(n/2))!.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =12a(5) =60a(6) =240a(7) =1680a(8) =18480a(9) =45360a(10) =574560a(11) =6320160a(12) =19293120a(13) =250810560a(14) =3615131520a(15) =10637827200a(16) =173837664000