Choulet-Curtz triangle with T(0,0)=1, T(n,n)=T(n,0).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =2a(6) =6a(7) =3a(8) =3a(9) =6a(10) =18a(11) =4a(12) =4a(13) =8a(14) =18a(15) =52a(16) =5a(17) =5a(18) =10a(19) =24a(20) =52a(21) =148a(22) =6a(23) =6a(24) =12a(25) =30a(26) =70a(27) =148a(28) =420a(29) =7