Generating function
$$U_{1173}(x, y) = \frac{\left(1 - y\right)^{9} \left(1 - \sqrt{- \frac{4 x}{\left(1 - y\right)^{3}} + 1}\right)^{3}}{8 x^{3}}$$
Explicit formula
$$T_{1173}(n, m, k) = \frac{3 k {\binom{3 k + 2 n - 1}{n}} {\binom{m + 3 n - 1}{m}}}{3 k + n}$$
Data table
1 0 0 0 0 0 0
3 9 18 3 45 63 84
9 54 189 504 1134 2268 4158
28 252 126 462 1386 36036 84084
9 108 702 3276 12285 39312 111384
297 4455 3564 20196 90882 3453516 1151172
1001 18018 171171 114114 5990985 26360334 101047947
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