Triangle read by rows: T(n,k) is the number of Dyck paths of semilength n having k exterior pairs.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =1a(5) =8a(6) =5a(7) =1a(8) =16a(9) =18a(10) =7a(11) =1a(12) =32a(13) =56a(14) =34a(15) =9a(16) =1a(17) =64a(18) =160a(19) =138a(20) =55a(21) =11a(22) =1a(23) =128a(24) =432a(25) =500a(26) =275a(27) =81a(28) =13a(29) =1