Number of permutations of length n which avoid the patterns 4213 and 2143.

A165537

Number of permutations of length n which avoid the patterns 4213 and 2143.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =88a(6) =366a(7) =1556a(8) =6720a(9) =29396a(10) =129996a(11) =580276a(12) =2611290a(13) =11834116a(14) =53963190a(15) =247414100a(16) =1139860150a(17) =5274189156a(18) =24498929370a(19) =114199276476a(20) =534028437710

External references