Number of permutations of length n which avoid the patterns 2314, 3421, 4123.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =72a(5) =229a(6) =683a(7) =1954a(8) =5452a(9) =14974a(10) =40671a(11) =109509a(12) =292743a(13) =777810a(14) =2055833a(15) =5409187a(16) =14175902a(17) =37020669a(18) =96378274a(19) =250204801a(20) =647907945a(21) =1673920904a(22) =4315683002a(23) =11105412898a(24) =28527156939a(25) =73161209063a(26) =187350573875