Triangle read by rows: T(n,k) = binomial(n*k,3) (0 <= k <= n).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =4a(6) =0a(7) =1a(8) =20a(9) =84a(10) =0a(11) =4a(12) =56a(13) =220a(14) =560a(15) =0a(16) =10a(17) =120a(18) =455a(19) =1140a(20) =2300a(21) =0a(22) =20a(23) =220a(24) =816a(25) =2024a(26) =4060a(27) =7140a(28) =0a(29) =35