Triangle: T(n,k)=C(4n-1,2k), 0<=k<=n.

Terms

a(0) =1a(1) =1a(2) =3a(3) =1a(4) =21a(5) =35a(6) =1a(7) =55a(8) =330a(9) =462a(10) =1a(11) =105a(12) =1365a(13) =5005a(14) =6435a(15) =1a(16) =171a(17) =3876a(18) =27132a(19) =75582a(20) =92378a(21) =1a(22) =253a(23) =8855a(24) =100947a(25) =490314a(26) =1144066a(27) =1352078a(28) =1a(29) =351