$$U_{207}(x, y) = \frac{y \left(x^{4} - 4 x^{3} + 6 x^{2} - 4 x + 1\right) + 1}{x^{2} - 2 x + 1}$$

$$T_{207}(n, m, k) = {\binom{k}{m}} {\binom{2 k - 4 m + n - 1}{n}}$$