Number of Wachs permutations of size n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =24a(6) =48a(7) =192a(8) =384a(9) =1920a(10) =3840a(11) =23040a(12) =46080a(13) =322560a(14) =645120a(15) =5160960a(16) =10321920a(17) =92897280a(18) =185794560a(19) =1857945600a(20) =3715891200a(21) =40874803200a(22) =81749606400a(23) =980995276800