$$U_{671}(x, y) = \sqrt{1 - 4 y} \left(x^{2} + \frac{2 x}{\sqrt{1 - 4 y}} + \frac{1}{1 - 4 y}\right)$$

$$T_{671}(n, m, k) = 4^{m} {\binom{2 k}{n}} {\binom{\frac{k}{2} + m - \frac{n}{2} - 1}{m}}$$