Number of permutations of length n which avoid the patterns 231, 3214, 4312.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =27a(5) =59a(6) =126a(7) =265a(8) =551a(9) =1136a(10) =2327a(11) =4743a(12) =9630a(13) =19493a(14) =39363a(15) =79336a(16) =159659a(17) =320915a(18) =644414a(19) =1293009a(20) =2592783a(21) =5196512a(22) =10410735a(23) =20850127a(24) =41746622a(25) =83568269a(26) =167257931a(27) =334712280a(28) =669742371a(29) =1339998971