Triangle, read by rows, T(n, k) = binomial(4*n, 3*k) + binomial(4*n, 3*(n-k)).

Terms

a(0) =2a(1) =5a(2) =5a(3) =29a(4) =112a(5) =29a(6) =221a(7) =1144a(8) =1144a(9) =221a(10) =1821a(11) =12000a(12) =16016a(13) =12000a(14) =1821a(15) =15505a(16) =127110a(17) =206720a(18) =206720a(19) =127110a(20) =15505a(21) =134597a(22) =1309528a(23) =2838752a(24) =2615008a(25) =2838752a(26) =1309528a(27) =134597a(28) =1184041a(29) =13126386