Number of lattice paths from (0,0) to (n,n) consisting of steps U=(1,1), H=(1,0) and S=(0,1) such that the first step leaving and the last step joining the diagonal (if any) is an H step.

A226996

Number of lattice paths from (0,0) to (n,n) consisting of steps U=(1,1), H=(1,0) and S=(0,1) such that the first step leaving and the last step joining the diagonal (if any) is an H step.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =10a(4) =59a(5) =339a(6) =1908a(7) =10660a(8) =59493a(9) =332469a(10) =1861910a(11) =10451086a(12) =58793535a(13) =331434215a(14) =1871929768a(15) =10590886536a(16) =60014622089a(17) =340566437545

External references