Number of permutations of length n which avoid the patterns 1234, 3421, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =70a(5) =177a(6) =333a(7) =538a(8) =792a(9) =1095a(10) =1447a(11) =1848a(12) =2298a(13) =2797a(14) =3345a(15) =3942a(16) =4588a(17) =5283a(18) =6027a(19) =6820a(20) =7662a(21) =8553a(22) =9493a(23) =10482a(24) =11520a(25) =12607a(26) =13743a(27) =14928a(28) =16162a(29) =17445