Number of permutations of [n] avoiding {2143, 4132, 1324}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =75a(6) =265a(7) =927a(8) =3229a(9) =11253a(10) =39355a(11) =138362a(12) =489440a(13) =1742576a(14) =6244395a(15) =22516585a(16) =81673947a(17) =297894234a(18) =1092086024a(19) =4022418903a(20) =14879231036a(21) =55255415912a(22) =205931156743a(23) =769994355746