$$G_{520}(x, y) = \frac{\sqrt{4 x + \left(y + 1\right)^{8}} + \left(y + 1\right)^{4}}{2 \left(y + 1\right)^{2}}$$

$$T_{520}(n, m, k) = \begin{cases}{\binom{2 k}{m}}&\text{if n==0} ,\ \\\frac{k {\binom{2 k - 8 n}{m}} {\binom{k - n - 1}{n - 1}}}{n}&\text{if n>0} \end{cases} $$