$$U_{659}(x, y) = \frac{1 - \sqrt{- 4 x \left(1 - \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{- y}}{2} \right)}}{3} \right)}}{3}\right)^{3} + 1}}{2 x \left(1 - \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{- y}}{2} \right)}}{3} \right)}}{3}\right)^{2}}$$

$$T_{659}(n, m, k) = \begin{cases}\frac{\left(-1\right)^{m - 1} k \left(k + 3 n\right) {\binom{k + 2 n - 1}{n}} {\binom{- k + 3 m - 3 n - 1}{m - 1}}}{m \left(k + n\right)}&\text{if m>0} ,\ \\\frac{k {\binom{k + 2 n - 1}{n}}}{k + n}&\text{if m=0} ,\ \\\frac{\left(-1\right)^{m - 1} k \left(k + 3 n\right) {\binom{k + 2 n - 1}{n}} {\binom{- k + 3 m - 3 n - 1}{m - 1}}}{m \left(k + n\right)} \end{cases} $$