a(0) = 0; for n>0, a(n) = 6*n!.

Terms

a(0) =0a(1) =6a(2) =12a(3) =36a(4) =144a(5) =720a(6) =4320a(7) =30240a(8) =241920a(9) =2177280a(10) =21772800a(11) =239500800a(12) =2874009600a(13) =37362124800a(14) =523069747200