$$U_{69}(x, y) = \frac{x - \sqrt{x^{2} + 2 x y \sqrt{1 - 4 x} - 2 x y}}{2 x y}$$

$$T_{69}(n, m, k) = \frac{k {\binom{k + 2 m - 1}{m}} {\binom{k + m + 2 n - 1}{n}}}{k + m + n}$$