a(n) is the number of permutations of length n that avoid the pattern 231 and the mesh pattern (12, 281) or the same sequence for the mesh patterns (12, 313), (12, 345), (12, 377), (12, 401), (12, 403), (12, 465), (12, 467).
A289449
a(n) is the number of permutations of length n that avoid the pattern 231 and the mesh pattern (12, 281) or the same sequence for the mesh patterns (12, 313), (12, 345), (12, 377), (12, 401), (12, 403), (12, 465), (12, 467).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =2a(4) =7a(5) =26a(6) =93a(7) =325a(8) =1129a(9) =3935a(10) =13813a(11) =48885a(12) =174397a(13) =626785a(14) =2267813a(15) =8254806a(16) =30209779a(17) =111094202a(18) =410327745a(19) =1521547078a(20) =5662360451a(21) =21141200004a(22) =79170069157a(23) =297293424680
External references
- oeis: A289449