Number of permutations of length n which avoid the patterns 1234 and 2341.

A165540

Number of permutations of length n which avoid the patterns 1234 and 2341.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =89a(6) =376a(7) =1611a(8) =6901a(9) =29375a(10) =123996a(11) =518971a(12) =2155145a(13) =8888348a(14) =36442184a(15) =148669894a(16) =603984658a(17) =2445184835a(18) =9870338447a(19) =39746337616a(20) =159728191141a(21) =640811439917

External references