Number of permutations of length n which avoid the patterns 4321 and 1324.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =86a(6) =332a(7) =1217a(8) =4140a(9) =12934a(10) =37088a(11) =98115a(12) =241269a(13) =555881a(14) =1208988a(15) =2498732a(16) =4936275a(17) =9367783a(18) =17151454a(19) =30408684a(20) =52373368a(21) =87869112a(22) =143950884a(23) =230755459a(24) =362614022a(25) =559490596a(26) =848821676a(27) =1267845697a(28) =1866525871a(29) =2711186627