Number of permutations of length n which avoid the patterns 2134, 3421, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =71a(5) =200a(6) =465a(7) =929a(8) =1667a(9) =2766a(10) =4325a(11) =6455a(12) =9279a(13) =12932a(14) =17561a(15) =23325a(16) =30395a(17) =38954a(18) =49197a(19) =61331a(20) =75575a(21) =92160a(22) =111329a(23) =133337a(24) =158451a(25) =186950a(26) =219125a(27) =255279a(28) =295727a(29) =340796