Number of permutations of [n] avoiding {1324, 1342, 3412}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =75a(6) =260a(7) =864a(8) =2756a(9) =8485a(10) =25365a(11) =74021a(12) =211814a(13) =596506a(14) =1658102a(15) =4560087a(16) =12431775a(17) =33648663a(18) =90537656a(19) =242420772a(20) =646489544a(21) =1718347081a(22) =4554820137a(23) =12046252361a(24) =31799943626a(25) =83818097710a(26) =220650496730a(27) =580264098939