$$U_{908}(x, y) = \frac{- 2 x - y - \sqrt{4 x^{2} - 4 x + y^{2} + y \left(- 4 x - 2\right) + 1} + 1}{4 x y}$$

$$T_{908}(n, m, k) = \frac{2^{n} k {\binom{k + m + n}{m}} {\binom{k + m + n}{n}}}{k + m + n}$$