Number of degree-n permutations of order exactly 4.

Terms

a(0) =0a(1) =0a(2) =0a(3) =6a(4) =30a(5) =180a(6) =840a(7) =5460a(8) =30996a(9) =209160a(10) =1290960a(11) =9753480a(12) =69618120a(13) =571627056a(14) =4443697440a(15) =40027718640a(16) =346953934320