$$U_{682}(x, y) = \frac{1 - \sqrt{\frac{4 x}{\sqrt{1 - 4 y}} + 1}}{2 x}$$

$$T_{682}(n, m, k) = \frac{\left(-1\right)^{- k + n} 4^{m} k {\binom{k + 2 n - 1}{k + n - 1}} {\binom{\frac{k}{2} + m + \frac{n}{2} - 1}{m}}}{k + n}$$