$$U_{728}(x, y) = \left(1 - \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{- x}}{2} \right)}}{3} \right)}}{3}\right)^{2} \left(y + 1\right)$$

$$T_{728}(n, m, k) = \begin{cases}\frac{2 \left(-1\right)^{n - 1} k {\binom{k}{m}} {\binom{- 2 k + 3 n - 1}{n - 1}}}{n}&\text{if n>0} ,\ \\{\binom{k}{m}}&\text{if n=0} \end{cases} $$