Number of permutations of length n which avoid the patterns 2314, 2431, 4123.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =72a(5) =228a(6) =670a(7) =1864a(8) =5000a(9) =13099a(10) =33789a(11) =86239a(12) =218432a(13) =550107a(14) =1379348a(15) =3446817a(16) =8590103a(17) =21362792a(18) =53037845a(19) =131501095a(20) =325690131a(21) =805941635a(22) =1992965105a(23) =4925514322a(24) =12167639830a(25) =30047049122a(26) =74176872249a(27) =183075826494