$$U_{656}(x, y) = \frac{\left(1 - \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{- y}}{2} \right)}}{3} \right)}}{3}\right) \left(\sqrt{4 x + 1} + 1\right)}{2}$$

$$T_{656}(n, m, k) = \begin{cases}1&\text{if n = 0,m = 0} ,\ \\\frac{\left(-1\right)^{m - 1} \left(-1\right)^{n - 1} k^{2} {\binom{- k + 3 m - 1}{m - 1}} {\binom{- k + 2 n - 1}{n - 1}}}{m n}&\text{if n > 0,m > 0} ,\ \\\frac{\left(-1\right)^{m - 1} k {\binom{- k + 3 m - 1}{m - 1}}}{m}&\text{if n = 0,m > 0} ,\ \\\frac{\left(-1\right)^{n - 1} k {\binom{- k + 2 n - 1}{n - 1}}}{n}&\text{if m = 0, n > 0} \end{cases} $$