Pyramid #988
Generating function
$$U_{988}(x, y) = \frac{1}{\left(y + 1\right)^{2} \left(- x \left(y + 1\right) + 1\right)}$$
Explicit formula
$$T_{988}(n, m, k) = {\binom{- 2 k + n}{m}} {\binom{k + n - 1}{n}}$$
Data table
1 -2 3 -4 5 -6 7
1 -1 1 -1 1 -1 1
1 0 0 0 0 0 0
1 1 0 0 0 0 0
1 2 1 0 0 0 0
1 3 3 1 0 0 0
1 4 6 4 1 0 0
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