The number of permutations of length n sortable by 3 cut-and-paste moves.

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =720a(6) =5040a(7) =36757a(8) =223898a(9) =1055479a(10) =3973264a(11) =12530496a(12) =34434065a(13) =84883448a(14) =191729212a(15) =403095882a(16) =798248632a(17) =1502630530a(18) =2708156958a(19) =4700026333a(20) =7891491375a(21) =12868232903a(22) =20444188490a(23) =31730911273a(24) =48222769794a(25) =71900547943