Number of permutations of length n which avoid the patterns 2341, 3241, 4132.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =74a(5) =257a(6) =881a(7) =2995a(8) =10132a(9) =34182a(10) =115143a(11) =387538a(12) =1303745a(13) =4384933a(14) =14746009a(15) =49585430a(16) =166730986a(17) =560620697a(18) =1885023706a(19) =6338138505a(20) =21311063589a(21) =71655198707a(22) =240929422288a(23) =810087129234