Pyramid #644
Generating function
$$U_{644}(x, y) = \frac{- \sqrt{4 y + 1} - 1}{x \sqrt{4 y + 1} + x - 2}$$
Explicit formula
$$T_{644}(n, m, k) = \begin{cases}{\binom{k + n - 1}{n}}&\text{if m==0} ,\ \\\frac{\left(-1\right)^{m - 1} k {\binom{k + n}{n}} {\binom{- k + 2 m - n - 1}{m - 1}}}{m}&\text{if m>0} \end{cases} $$
Data table
1 1 -1 2 -5 14 -42
1 2 -1 2 -5 14 -42
1 3 0 1 -3 9 -28
1 4 2 0 -1 4 -14
1 5 5 0 0 1 -5
1 6 9 2 0 0 -1
1 7 14 7 0 0 0
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