Pyramid #344
Generating function
$$U_{344}(x, y) = \frac{\frac{2 x}{3} + \frac{1}{9 \left(1 - y\right)^{2}}}{\sqrt[3]{\frac{x^{2} \left(1 - y\right)}{2} + \frac{\sqrt{3} x \sqrt{x \left(27 x + \frac{4}{\left(1 - y\right)^{2}}\right)} \left(1 - y\right)}{18} + \frac{x}{3 - 3 y} + \frac{1}{27 \left(1 - y\right)^{3}}}} + \sqrt[3]{\frac{x^{2} \left(1 - y\right)}{2} + \frac{\sqrt{3} x \sqrt{x \left(27 x + \frac{4}{\left(1 - y\right)^{2}}\right)} \left(1 - y\right)}{18} + \frac{x}{3 - 3 y} + \frac{1}{27 \left(1 - y\right)^{3}}} + \frac{1}{3 - 3 y}$$
Explicit formula
$$T_{344}(n, m, k) = \begin{cases}{\binom{k + m - 1}{m}}&\text{if n=0} ,\ \\\frac{2 k {\binom{2 k - 2 n - 1}{n - 1}} {\binom{k + m - 2 n - 1}{m}}}{n} \end{cases} $$
Data table
1 1 1 1 1 1 1
2 -2 0 0 0 0 0
-3 9 -9 3 0 0 0
1 -5 1 -1 5 -1 0
-42 294 -882 147 -147 882 -294
198 -1782 7128 -16632 24948 -24948 16632
-1001 11011 -55055 165165 -33033 462462 -462462
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