Number of permutations which avoid the patterns 1324 and (2143 with Bruhat restriction {2<->3}). Also the number of permutations whose graphs are acyclic.

A111053

Number of permutations which avoid the patterns 1324 and (2143 with Bruhat restriction {2<->3}). Also the number of permutations whose graphs are acyclic.

Terms

    a(0) =1a(1) =2a(2) =6a(3) =22a(4) =89a(5) =379a(6) =1661a(7) =7405a(8) =33367a(9) =151398a(10) =690147a(11) =3156112a(12) =14465746a(13) =66409493a(14) =305232025a(15) =1404129530a(16) =6463476538a(17) =29767212095a(18) =137142651679a(19) =632021380433

External references