a(n) is the greatest common divisor of (n-1)! and n^n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =1a(5) =24a(6) =1a(7) =16a(8) =9a(9) =640a(10) =1a(11) =20736a(12) =1a(13) =7168a(14) =6075a(15) =2048a(16) =1a(17) =23887872a(18) =1a(19) =8192000a(20) =321489a(21) =2883584a(22) =1a(23) =10319560704a(24) =625a(25) =54525952a(26) =59049a(27) =2877292544a(28) =1a(30) =1