Pyramid #384
Generating function
$$U_{384}(x, y) = - \frac{\sqrt{\frac{4 x}{1 - y} + \frac{1}{\left(1 - y\right)^{2}}}}{2} + \frac{1}{2 - 2 y}$$
Explicit formula
$$T_{384}(n, m, k) = \begin{cases}0&\text{if n<k} ,\ \\- \frac{k {\binom{k - n - 1}{n - 1}} {\binom{k + m - n - 1}{m}}}{n} \end{cases} $$
Data table
0 0 0 0 0 0 0
-1 0 0 0 0 0 0
1 -1 0 0 0 0 0
-2 4 -2 0 0 0 0
5 -15 15 -5 0 0 0
-14 56 -84 56 -14 0 0
42 -21 42 -42 21 -42 0
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