$$U_{884}(x, y) = \frac{2 - 2 \cos{\left(\frac{2 \arcsin{\left(\frac{3 \sqrt{3} \sqrt{x} \operatorname{abs}{\left(y + 1 \right)}}{2} \right)}}{3} \right)}}{3 x \left(y + 1\right)}$$

$$T_{884}(n, m, k) = \frac{k {\binom{k + 2 n}{m}} {\binom{2 k + 3 n - 1}{n}}}{k + n}$$