Number of permutations of length n which avoid the patterns 2341 and 3421.

A165545

Number of permutations of length n which avoid the patterns 2341 and 3421.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =89a(6) =382a(7) =1711a(8) =7922a(9) =37663a(10) =182936a(11) =904302a(12) =4535994a(13) =23034564a(14) =118209806a(15) =612165222a(16) =3195359360a(17) =16795435994a(18) =88825567814a(19) =472356139660

External references