Number of permutations of length n which avoid the patterns 2134, 2143, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =73a(5) =239a(6) =734a(7) =2134a(8) =5934a(9) =15918a(10) =41470a(11) =105470a(12) =262910a(13) =644350a(14) =1556478a(15) =3713022a(16) =8761342a(17) =20475902a(18) =47448062a(19) =109117438a(20) =249233406a(21) =565772286a(22) =1277165566a(23) =2868379646a(24) =6412042238a(25) =14272167934a(26) =31641829374a(27) =69893881854a(28) =153863847934a(29) =337641471998