$$U_{71}(x, y) = \frac{y^{2} - 2 y - \sqrt{- 4 x + y^{4} - 4 y^{3} + 6 y^{2} - 4 y + 1} + 1}{2 x}$$

$$T_{71}(n, m, k) = \frac{k {\binom{k + 2 n - 1}{n}} {\binom{2 k + m + 4 n - 1}{m}}}{k + n}$$