a(n) = A056623(n!).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =144a(6) =144a(7) =144a(8) =1296a(9) =518400a(10) =518400a(11) =230400a(12) =230400a(13) =2822400a(14) =9144576a(15) =146313216a(16) =146313216a(17) =21069103104a(18) =21069103104a(20) =119439360000