Number of permutations of [n] avoiding {1243, 1324, 2431}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =77a(6) =283a(7) =1032a(8) =3740a(9) =13522a(10) =48930a(11) =177564a(12) =646908a(13) =2367121a(14) =8699706a(15) =32108614a(16) =118975273a(17) =442467434a(18) =1651076429a(19) =6180073782a(20) =23197995681a(21) =87304824502a(22) =329357941951