$$U_{481}(x, y) = \frac{\left(y + 1\right)^{2} \left(- 2 x - \sqrt{1 - 4 x} + 1\right)}{2 x^{2}}$$

$$T_{481}(n, m, k) = \frac{k {\binom{2 k}{m}} {\binom{2 k + 2 n}{n}}}{k + n}$$