a(n) = lcm(n^2, n!).

Terms

a(0) =0a(1) =1a(2) =4a(3) =18a(4) =48a(5) =600a(6) =720a(7) =35280a(8) =40320a(9) =362880a(10) =3628800a(11) =439084800a(12) =479001600a(13) =80951270400a(14) =87178291200