$$U_{731}(x, y) = \frac{- 2 x y^{2} - 4 x y - 2 x - \sqrt{- 4 x y^{2} - 8 x y - 4 x + 1} + 1}{2 x^{2} y^{3} + 6 x^{2} y^{2} + 6 x^{2} y + 2 x^{2}}$$

$$T_{731}(n, m, k) = \frac{k {\binom{k + 2 n}{m}} {\binom{2 k + 2 n}{n}}}{k + n}$$