$$U_{899}(x, y) = \frac{\left(1 - y\right) \left(2 - 2 \cos{\left(\frac{2 \arcsin{\left(\frac{3 \sqrt{3} \sqrt{x}}{2 \operatorname{abs}{\left(y - 1 \right)}} \right)}}{3} \right)}\right)}{3 x}$$

$$T_{899}(n, m, k) = \frac{k {\binom{2 k + 3 n - 1}{n}} {\binom{k + m + 2 n - 1}{m}}}{k + n}$$