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
$$T_{478}(n, m, k) = \begin{cases}\frac{k {\binom{k - n - 1}{n - 1}}}{n}&\text{if n>0 and m=0} ,\ \\\frac{k {\binom{k + 3 m - 1}{m}}}{k + 2 m}&\text{if n=0 and m>0} ,\ \\\frac{\left(-1\right)^{m - 1} k \left(k - 3 n\right) {\binom{k - n - 1}{n - 1}} {\binom{- k - 2 m + 3 n - 1}{m - 1}}}{m n}&\text{if n>0 and m>0} ,\ \\1&\text{if n=0 and m=0} \end{cases} $$
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 |
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