Pyramid #1044
Pyramid #1045
Pyramid #1046
Generating function
$$U_{1045}(x, y) = \frac{1}{\left(1 - x\right)^{3} \left(1 - y\right)^{3}}$$
Explicit formula
$$T_{1045}(n, m, k) = {\binom{3 k + m - 1}{m}} {\binom{3 k + n - 1}{n}}$$
Data table
1 3 6 1 15 21 28
3 9 18 3 45 63 84
6 18 36 6 9 126 168
1 3 6 1 15 21 28
15 45 9 15 225 315 42
21 63 126 21 315 441 588
28 84 168 28 42 588 784
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