Number of permutations of [n] avoiding {1243, 1324, 3412}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =73a(6) =237a(7) =711a(8) =1988a(9) =5253a(10) =13301a(11) =32673a(12) =78669a(13) =187230a(14) =443398a(15) =1050209a(16) =2497187a(17) =5976456a(18) =14419577a(19) =35101838a(20) =86229874a(21) =213707024a(22) =534022585a(23) =1344450284a(24) =3407215499a(25) =8684458421a(26) =22243751970a(27) =57208235104a(28) =147636483121a(29) =382077767531