$$U_{418}(x, y) = \frac{y + \sqrt{- 4 x + y^{2} - 2 y + 1} - 1}{2 x y - 2 x}$$

$$T_{418}(n, m, k) = \begin{cases}\frac{k {\binom{k + 2 n - 1}{n}} {\binom{2 k + m + 2 n - 1}{m}}}{k + n},\ \\0,\ \\0,\ \\0 \end{cases} $$