Number of preimages of 321-avoiding permutations of [n] under West's stack-sorting map.
A319027
Number of preimages of 321-avoiding permutations of [n] under West's stack-sorting map.
Terms
- a(0) =1a(1) =2a(2) =6a(3) =24a(4) =117a(5) =652a(6) =3988a(7) =26112a(8) =180126a(9) =1295090a(10) =9631656a(11) =73676572a(12) =577180996a(13) =4615090192a(14) =37562920238a(15) =310523535692
External references
- oeis: A319027