Number of permutations of [n] avoiding {4231, 1423, 1234}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =74a(6) =245a(7) =744a(8) =2068a(9) =5296a(10) =12608a(11) =28150a(12) =59412a(13) =119341a(14) =229477a(15) =424478a(16) =758491a(17) =1313931a(18) =2213350a(19) =3635214a(20) =5834559a(21) =9169668a(22) =14136101a(23) =21409620a(24) =31899782a(25) =46816226a(26) =67749956a(27) =96772222a(28) =136553926a(29) =190508831