Number of permutations of length n which avoid the patterns 2314, 4321.

Terms

a(0) =1a(1) =2a(2) =6a(3) =22a(4) =86a(5) =330a(6) =1198a(7) =4087a(8) =13185a(9) =40619a(10) =120636a(11) =348197a(12) =983073a(13) =2728722a(14) =7475575a(15) =20274288a(16) =54558291a(17) =145933414a(18) =388520823a(19) =1030601705a(20) =2726043970a(21) =7194657991a(22) =18955376065a(23) =49872709551a(24) =131077883030a(25) =344216450494a(26) =903332924312