a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 431) or the same sequence for the mesh pattern (12, 491).
A289601
a(n) is the number of permutations of length n that avoid the pattern 321 and the mesh pattern (12, 431) or the same sequence for the mesh pattern (12, 491).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =3a(4) =10a(5) =34a(6) =114a(7) =382a(8) =1292a(9) =4426a(10) =15358a(11) =53915a(12) =191206a(13) =684103a(14) =2466416a(15) =8951932a(16) =32683216a(17) =119949930a(18) =442281014a(19) =1637618383a(20) =6086481702a(21) =22699003811a(22) =84918443200a(23) =318593346609
External references
- oeis: A289601