Number of permutations of length n which avoid the patterns 1243, 1432, 4213.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =73a(5) =242a(6) =772a(7) =2409a(8) =7439a(9) =22872a(10) =70204a(11) =215345a(12) =660375a(13) =2024866a(14) =6208416a(15) =19035179a(16) =58361985a(17) =178937794a(18) =548622648a(19) =1682074579a(20) =5157232471a(21) =15812048862a(22) =48479661510a(23) =148638395025a(24) =455724560391