Generating function
$$U_{416}(x, y) = \frac{\sqrt{4 y + 1}}{6} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{2}}{36 \sqrt[3]{\frac{x}{2} + \frac{\sqrt{3} \sqrt{x \left(27 x + \frac{\left(\sqrt{4 y + 1} + 1\right)^{3}}{2}\right)}}{18} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{3}}{216}}} + \sqrt[3]{\frac{x}{2} + \frac{\sqrt{3} \sqrt{x \left(27 x + \frac{\left(\sqrt{4 y + 1} + 1\right)^{3}}{2}\right)}}{18} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{3}}{216}} + \frac{1}{6}$$
Explicit formula
$$T_{416}(n, m, k) = \begin{cases}1&\text{if n=0 and m=0} ,\ \\\frac{k {\binom{k - 2 n - 1}{n - 1}}}{n}&\text{if n>0} ,\ \\\frac{\left(-1\right)^{m - 1} k {\binom{k - 2 n - 1}{n}} {\binom{- k + 2 m + 3 n - 1}{m - 1}}}{m} \end{cases} $$
1 | -1 | -1/2 | -8/3 | -17/4 | -66/5 | -85/2 |
1 | 1 | 1 | 1 | 1 | 1 | 1 |
-2 | -2 | -2 | -2 | -2 | -2 | -2 |
7 | 7 | 7 | 7 | 7 | 7 | 7 |
-3 | -3 | -3 | -3 | -3 | -3 | -3 |
143 | 143 | 143 | 143 | 143 | 143 | 143 |
-728 | -728 | -728 | -728 | -728 | -728 | -728 |
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