Number of permutations of length n that avoid the patterns 4231, 4312, and 4321.

A257561

Number of permutations of length n that avoid the patterns 4231, 4312, and 4321.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =80a(6) =322a(7) =1346a(8) =5783a(9) =25372a(10) =113174a(11) =511649a(12) =2338988a(13) =10793251a(14) =50205607a(15) =235156609a(16) =1108120540a(17) =5249646137a(18) =24987770893a(19) =119443412277a(20) =573125649031

External references