Number of permutations of length n which avoid the patterns 4231 and 4123.

A165542

Number of permutations of length n which avoid the patterns 4231 and 4123.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =89a(6) =380a(7) =1677a(8) =7566a(9) =34676a(10) =160808a(11) =752608a(12) =3548325a(13) =16830544a(14) =80234659a(15) =384132724a(16) =1845829988a(17) =8897740300a(18) =43010084460a(19) =208409687323

External references