$$U_{956}(x, y) = \frac{1 - \sqrt{1 - 4 \left(x + y\right)^{2}}}{2 \left(x + y\right)^{2}}$$

$$T_{956}(n, m, k) = \begin{cases}\frac{2 k {\binom{m + n}{m}} {\binom{k + m + n - 1}{\frac{m}{2} + \frac{n}{2}}}}{2 k + m + n}&\text{if n + m even} ,\ \\0 \end{cases} $$