Triangle T(n, k) = binomial(n*k, n-k) + binomial(n*(n-k), k), read by rows.

Terms

a(0) =2a(1) =1a(2) =1a(3) =1a(4) =4a(5) =1a(6) =1a(7) =9a(8) =9a(9) =1a(10) =1a(11) =16a(12) =56a(13) =16a(14) =1a(15) =1a(16) =25a(17) =225a(18) =225a(19) =25a(20) =1a(21) =1a(22) =36a(23) =771a(24) =1632a(25) =771a(26) =36a(27) =1a(28) =1a(29) =49