Number of permutations of length n which avoid the patterns 1234, 1243, 3241.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =73a(5) =238a(6) =724a(7) =2078a(8) =5706a(9) =15161a(10) =39319a(11) =100168a(12) =251846a(13) =627046a(14) =1549898a(15) =3810125a(16) =9328073a(17) =22766362a(18) =55432684a(19) =134725294a(20) =326982110a(21) =792733065a(22) =1920267887a(23) =4648446316a(24) =11246721414a(25) =27199650590a(26) =65759222454a(27) =158940539445