Pyramid #432
Generating function
$$U_{432}(x, y) = \sqrt[3]{\frac{x}{2} + \frac{\sqrt{3} \sqrt{x \left(27 x + \frac{32 \sqrt{3} \sin^{3}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{9 y^{\frac{3}{2}}}\right)}}{18} + \frac{8 \sqrt{3} \sin^{3}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{243 y^{\frac{3}{2}}}} + \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{27 y \sqrt[3]{\frac{x}{2} + \frac{\sqrt{3} \sqrt{x \left(27 x + \frac{32 \sqrt{3} \sin^{3}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{9 y^{\frac{3}{2}}}\right)}}{18} + \frac{8 \sqrt{3} \sin^{3}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{243 y^{\frac{3}{2}}}}} + \frac{2 \sqrt{3} \sin{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{9 \sqrt{y}}$$
Explicit formula
$$T_{432}(n, m, k) = \begin{cases}1&\text{if n=0 and m=0} ,\ \\\frac{k {\binom{k + 3 m - n - 1}{m}}}{k + 2 m}&\text{if n=0} ,\ \\\frac{\left(-1\right)^{n - 1} k {\binom{- k + 3 n - 1}{n - 1}}}{n}&\text{if m=0} ,\ \\\frac{\left(-1\right)^{m - 1} k \left(k - 3 n\right) {\binom{k - 2 n - 1}{n - 1}} {\binom{- k - 2 m + 3 n - 1}{m - 1}}}{m n}&\text{if m>0} \end{cases} $$
Data table
1 1 3 12 55 273 1428
1 -2 -3 -1 -42 -198 -1001
-2 1 0 1 5 252 132
7 -56 84 0 -14 -168 -1176
-3 33 -99 66 0 0 33
143 -2002 9009 -14014 5005 0 0
-728 12376 -74256 18564 -173264 37128 0
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