$$U_{246}(x, y) = \frac{- \sqrt{- 4 x^{2} y^{2} + 4 x^{2} + 1} - 1}{2 y^{2} - 2}$$

$$T_{246}(n, m, k) = \frac{\left(-1\right)^{\frac{m}{2} + \frac{n}{2} + 1} k \left(\left(-1\right)^{m} + 1\right) \left(\left(-1\right)^{n} + 1\right) {\binom{\frac{m}{2} + \frac{n}{2}}{\frac{n}{2}}} {\binom{- k + n - 1}{\frac{m}{2} + \frac{n}{2} - 1}}}{2 m + 2 n}$$