Number of permutations of length n which avoid the patterns 2134, 3241, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =73a(5) =236a(6) =705a(7) =1970a(8) =5224a(9) =13307a(10) =32866a(11) =79251a(12) =187523a(13) =437030a(14) =1005935a(15) =2291536a(16) =5174458a(17) =11596189a(18) =25816552a(19) =57141641a(20) =125822061a(21) =275766912a(22) =601872301a(23) =1308610526a(24) =2835334908a(25) =6123666671a(26) =13186871710a(27) =28319917295