Pyramid #478
Generating function
$$U_{478}(x, y) = \frac{\sqrt{3} \sqrt{y} \left(\sqrt{\frac{8 \sqrt{3} x \sin{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{3 \sqrt{y}} + \frac{16 \sin^{4}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{9 y^{2}}} + \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}{3 y}\right)}{4 \sin{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{y}}{2} \right)}}{3} \right)}}$$
Explicit formula
$$T_{478}(n, m, k) = \begin{cases}\frac{k {\binom{k - n - 1}{n - 1}}}{n}&\text{if n>0 and m=0} ,\ \\\frac{k {\binom{k + 3 m - 1}{m}}}{k + 2 m}&\text{if n=0 and m>0} ,\ \\\frac{\left(-1\right)^{m - 1} k \left(k - 3 n\right) {\binom{k - n - 1}{n - 1}} {\binom{- k - 2 m + 3 n - 1}{m - 1}}}{m n}&\text{if n>0 and m>0} ,\ \\1&\text{if n=0 and m=0} \end{cases} $$
Data table
1 1 3 12 55 273 1428
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
Export
expand_less