Number of permutations in S_n avoiding {bar 5}2143 (i.e., every occurrence of 2143 is contained in an occurrence of a 52143).

A137545

Number of permutations in S_n avoiding {bar 5}2143 (i.e., every occurrence of 2143 is contained in an occurrence of a 52143).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =23a(5) =104a(6) =535a(7) =3081a(8) =19737a(9) =140454a(10) =1111136a(11) =9777465a(12) =95587370a(13) =1034517225a(14) =12324487009a(15) =160503772329

External references