The number of permutations of length n sortable by 2 cut-and-paste moves.

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =577a(6) =2208a(7) =6768a(8) =17469a(9) =39603a(10) =81272a(11) =154225a(12) =274802a(13) =464985a(14) =753556a(15) =1177362a(16) =1782687a(17) =2626731a(18) =3779196a(19) =5323979a(20) =7360972a(21) =10007969a(22) =13402680a(23) =17704852a(24) =23098497a(25) =29794227a(26) =38031696a(27) =48082149a(28) =60251078a(29) =74880985