Number of permutations of length n which avoid the patterns 2341, 4132, 4321.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =72a(5) =233a(6) =739a(7) =2343a(8) =7458a(9) =23801a(10) =76016a(11) =242777a(12) =775265a(13) =2475513a(14) =7904587a(15) =25240597a(16) =80598107a(17) =257366469a(18) =821825201a(19) =2624260190a(20) =8379812195a(21) =26758495711a(22) =85445488885a(23) =272845382481a(24) =871252605664