$$U_{249}(x, y) = \frac{1}{- x - y^{2} + 1}$$

$$T_{249}(n, m, k) = \frac{\left(\left(-1\right)^{m} + 1\right) {\binom{\frac{m}{2} + n}{n}} {\binom{k + \frac{m}{2} + n - 1}{\frac{m}{2} + n}}}{2}$$