$$U_{126}(x, y) = \frac{2 x y + \sqrt{y^{2} \left(4 x^{2} + 1\right) - 2 y + 1}}{\left(1 - y\right)^{2}}$$

$$T_{126}(n, m, k) = \frac{4^{n} k {\binom{\frac{k}{2} + \frac{n}{2}}{n}} {\binom{k + m}{k + n}}}{k + m}$$