Triangle T(n,k) = binomial(4*n - 3*k, 3*n - 2*k), 0 <= k <= n.

Terms

a(0) =1a(1) =4a(2) =1a(3) =28a(4) =5a(5) =1a(6) =220a(7) =36a(8) =6a(9) =1a(10) =1820a(11) =286a(12) =45a(13) =7a(14) =1a(15) =15504a(16) =2380a(17) =364a(18) =55a(19) =8a(20) =1a(21) =134596a(22) =20349a(23) =3060a(24) =455a(25) =66a(26) =9a(27) =1a(28) =1184040a(29) =177100