Number of permutations of length n which avoid the patterns 4213 and 3421.

A165539

Number of permutations of length n which avoid the patterns 4213 and 3421.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =88a(6) =367a(7) =1571a(8) =6861a(9) =30468a(10) =137229a(11) =625573a(12) =2881230a(13) =13388094a(14) =62688448a(15) =295504025a(16) =1401195334a(17) =6678877732a(18) =31984089193a(19) =153809536017a(20) =742462191363

External references