Generating function
$$U_{1146}(x, y) = \frac{1}{\left(- \frac{x}{1 - y} + 1\right)^{3}}$$
Explicit formula
$$T_{1146}(n, m, k) = {\binom{3 k + n - 1}{n}} {\binom{m + n - 1}{m}}$$
Data table
1 0 0 0 0 0 0
3 3 3 3 3 3 3
6 12 18 24 3 36 42
1 3 6 1 15 21 28
15 6 15 3 525 84 126
21 105 315 735 147 2646 441
28 168 588 1568 3528 7056 12936
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