Number of permutations of length n which avoid the patterns 1342, 3421, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =72a(5) =233a(6) =719a(7) =2146a(8) =6260a(9) =17968a(10) =50967a(11) =143278a(12) =399960a(13) =1110203a(14) =3067479a(15) =8442903a(16) =23163006a(17) =63371999a(18) =172967309a(19) =471115792a(20) =1280844662a(21) =3476636122a(22) =9423007521a(23) =25506378316a(24) =68958653982a(25) =186231636833