$$U_{598}(x, y) = \frac{- y^{2} - 1}{x \left(y^{2} + 1\right)^{3} - 1}$$

$$T_{598}(n, m, k) = \frac{\left(\left(-1\right)^{m} + 1\right) {\binom{k + 3 n}{\frac{m}{2}}} {\binom{k + n - 1}{n}}}{2}$$