$$U_{724}(x, y) = \frac{- 2 x y^{3} - 6 x y^{2} - 6 x y - 2 x - \sqrt{- 4 x y^{3} - 12 x y^{2} - 12 x y - 4 x + 1} + 1}{2 x^{2} y^{2} + 4 x^{2} y + 2 x^{2}}$$

$$T_{724}(n, m, k) = \frac{k {\binom{2 k + 2 n}{n}} {\binom{4 k + 3 n}{m}}}{k + n}$$