$$U_{67}(x, y) = \frac{- y + \sqrt{4 x y + 2 x \sqrt{1 - 4 y} - 2 x + y^{2}}}{x \left(\sqrt{1 - 4 y} - 1\right)}$$

$$T_{67}(n, m, k) = \frac{k {\binom{k + 2 n}{n}} {\binom{k + 2 m + 2 n - 1}{m}}}{k + m + 2 n}$$