$$U_{804}(x, y) = \frac{\left(1 - y\right)^{2} \left(- \frac{2 x}{1 - y} - \sqrt{- \frac{4 x}{1 - y} + 1} + 1\right)}{2 x^{2}}$$

$$T_{804}(n, m, k) = \frac{k {\binom{2 k + 2 n}{n}} {\binom{m + n - 1}{m}}}{k + n}$$