Number of permutations of length n which avoid the patterns 2134, 3214, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =74a(5) =246a(6) =763a(7) =2227a(8) =6191a(9) =16567a(10) =43026a(11) =109110a(12) =271384a(13) =664236a(14) =1603813a(15) =3827381a(16) =9040909a(17) =21164253a(18) =49147156a(19) =113305760a(20) =259515246a(21) =590863722a(22) =1337972351a(23) =3014643351a(24) =6761203099a(25) =15099476851a(26) =33587965958a(27) =74440483642