Number of permutations of length n which avoid the patterns 2341, 3241, 4213.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =75a(5) =264a(6) =914a(7) =3127a(8) =10621a(9) =35932a(10) =121324a(11) =409301a(12) =1380417a(13) =4655382a(14) =15700590a(15) =52954137a(16) =178609067a(17) =602449564a(18) =2032105066a(19) =6854506171a(20) =23121097405a(21) =77990499392a(22) =263072412420a(23) =887378656761