Number of level permutations of degree n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =18a(5) =45a(6) =360a(7) =1575a(8) =20790a(9) =99225a(10) =1332450a(11) =9823275a(12) =181496700a(13) =1404728325a(14) =26221595400a(15) =273922023375