Triangle read by rows: T(n,k) is the number of ballotlike paths ending at (n, k), with 0 <= k <= n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =3a(8) =2a(9) =1a(10) =5a(11) =9a(12) =6a(13) =3a(14) =1a(15) =14a(16) =28a(17) =21a(18) =10a(19) =4a(20) =1a(21) =42a(22) =90a(23) =76a(24) =39a(25) =15a(26) =5a(27) =1a(28) =132a(29) =297