Number of permutations of [n] avoiding {2341, 2143, 4123}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =70a(6) =212a(7) =597a(8) =1610a(9) =4248a(10) =11107a(11) =28966a(12) =75552a(13) =197251a(14) =515476a(15) =1348060a(16) =3527067a(17) =9230832a(18) =24162270a(19) =63251763a(20) =165587512a(21) =433503706a(22) =1134914677a(23) =2971229196a(24) =7778759206a(25) =20365031725a(26) =53316315822a(27) =139583891642a(28) =365435330505a(29) =956722066178