$$U_{886}(x, y) = x \left(y + 1\right) + \frac{y}{2} + \frac{\sqrt{4 x + 1} \left(y + 1\right)}{2} + \frac{1}{2}$$

$$T_{886}(n, m, k) = \begin{cases}{\binom{k}{m}}&\text{if n=0} ,\ \\\frac{2 \left(-1\right)^{n - 1} k {\binom{k}{m}} {\binom{- 2 k + 2 n - 1}{n - 1}}}{n} \end{cases} $$