$$U_{605}(x, y) = \frac{- \sqrt{4 x + \frac{\left(\sqrt{4 y + 1} + 1\right)^{4}}{16}} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{2}}{4}}{\sqrt{4 y + 1} + 1}$$

$$T_{605}(n, m, k) = \begin{cases}0&\text{if n<k} ,\ \\- \frac{\left(-1\right)^{m - 1} k \left(k - 4 n\right) {\binom{k - n - 1}{n - 1}} {\binom{- k + 2 m + 4 n - 1}{m - 1}}}{m n}&\text{if m>0} ,\ \\- \frac{k {\binom{k - n - 1}{n - 1}}}{n}&\text{if m=0} \end{cases} $$