$$U_{244}(x, y) = \frac{1}{- x^{2} - y^{2} + 1}$$

$$T_{244}(n, m, k) = \frac{\left(\left(-1\right)^{m} + 1\right) \left(\left(-1\right)^{n} + 1\right) {\binom{\frac{m}{2} + \frac{n}{2}}{\frac{n}{2}}} {\binom{k + \frac{m}{2} + \frac{n}{2} - 1}{\frac{m}{2} + \frac{n}{2}}}}{4}$$