Pyramid #479
Generating function
$$U_{479}(x, y) = \frac{\sqrt{3} \sqrt{y} \left(- \sqrt{\frac{8 \sqrt{3} x \sin{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{3 \sqrt{y}} + \frac{16 \sin^{4}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{9 y^{2}}} + \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{3 y}\right)}{4 \sin{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}$$
Explicit formula
$$T_{479}(n, m, k) = \begin{cases}0&\text{if n<k} ,\ \\- \frac{{\binom{k - n - 1}{n - 1}}}{n}&\text{if m=0} ,\ \\- \frac{\left(-1\right)^{m - 1} \left(k - 3 n\right) {\binom{k - n - 1}{n - 1}} {\binom{- k - 2 m + 3 n - 1}{m - 1}}}{m n}&\text{if m>0} \end{cases} $$
Data table
0 0 0 0 0 0 0
-1 2 3 1 42 198 1001
1 -5 0 -5 -25 -126 -66
-2 16 -24 0 4 48 336
5 -55 165 -11 0 0 -55
-14 196 -882 1372 -49 0 0
42 -714 4284 -1071 9996 -2142 0
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