Number of permutations of [n] avoiding {4312, 1432, 1234}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =74a(6) =248a(7) =784a(8) =2355a(9) =6785a(10) =18897a(11) =51177a(12) =135358a(13) =350788a(14) =893038a(15) =2237998a(16) =5530485a(17) =13496371a(18) =32566359a(19) =77785039a(20) =184083080a(21) =432004206a(22) =1006097772a(23) =2326777196a(24) =5346673751a(25) =12213795349a(26) =27749494413a(27) =62729986469a(28) =141146690370a(29) =316216935240