$$U_{675}(x, y) = \frac{\sqrt{\frac{4 x}{\left(1 - y\right)^{2}} + 1} - 1}{2 x}$$

$$T_{675}(n, m, k) = \frac{\left(-1\right)^{n} k {\binom{k + 2 n - 1}{k + n - 1}} {\binom{2 k + m + 2 n - 1}{m}}}{k + n}$$