Number of permutations of length n which avoid the patterns 4312 and 1324.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =86a(6) =335a(7) =1266a(8) =4598a(9) =16016a(10) =53579a(11) =172663a(12) =537957a(13) =1626504a(14) =4789128a(15) =13777002a(16) =38833685a(17) =107531833a(18) =293178623a(19) =788633906a(20) =2096774922a(21) =5519058020a(22) =14402858655a(23) =37314455547a(24) =96088754649a(25) =246213555740a(26) =628392990988