$$U_{320}(x, y) = \frac{1 - \sqrt{4 x y^{6} - 24 x y^{5} + 60 x y^{4} - 80 x y^{3} + 60 x y^{2} - 24 x y + 4 x + 1}}{2 y^{2} - 4 y + 2}$$

$$T_{320}(n, m, k) = \begin{cases}0&\text{if n<k} ,\ \\- \frac{k {\binom{k - n - 1}{n - 1}} {\binom{2 k + m - 6 n - 1}{m}}}{n} \end{cases} $$