Triangle read by rows: T(n,k) is the number of Dyck n-paths whose first descent has length k.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =1a(5) =1a(6) =9a(7) =3a(8) =1a(9) =1a(10) =28a(11) =9a(12) =3a(13) =1a(14) =1a(15) =90a(16) =28a(17) =9a(18) =3a(19) =1a(20) =1a(21) =297a(22) =90a(23) =28a(24) =9a(25) =3a(26) =1a(27) =1a(28) =1001a(29) =297