Number of permutations of length n which avoid the patterns 2134, 3241, 4132.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =72a(5) =230a(6) =692a(7) =2004a(8) =5683a(9) =15948a(10) =44523a(11) =123924a(12) =344113a(13) =953353a(14) =2635064a(15) =7266192a(16) =19990484a(17) =54876361a(18) =150331490a(19) =411034895a(20) =1121843295a(21) =3056805471a(22) =8316456845a(23) =22593934835a(24) =61301610481a(25) =166118362404a(26) =449639670226