$$U_{913}(x, y) = \frac{1 - \sqrt{y \left(- 8 x^{2} - 16 x - 8\right) + 1}}{y \left(4 x + 4\right)}$$

$$T_{913}(n, m, k) = \frac{2^{m} k {\binom{k + 2 m}{m}} {\binom{k + 2 m}{n}}}{k + 2 m}$$