Number of returns to the x-axis in all hill-free Dyck paths of semilength n (a Dyck path is said to be hill-free if it has no peaks at level 1).

A114495

Number of returns to the x-axis in all hill-free Dyck paths of semilength n (a Dyck path is said to be hill-free if it has no peaks at level 1).

Terms

    a(0) =0a(1) =1a(2) =2a(3) =7a(4) =22a(5) =73a(6) =246a(7) =844a(8) =2936a(9) =10334a(10) =36736a(11) =131709a(12) =475714a(13) =1729345a(14) =6322534a(15) =23232616a(16) =85757008a(17) =317839438a(18) =1182341740a(19) =4412949358a(20) =16521076012a(21) =62024023306a(22) =233451103612a(23) =880764587512

External references