$$U_{226}(x, y) = x + \frac{y \left(- 2 x - \sqrt{1 - 4 x} + 1\right)}{2 x^{2}}$$

$$T_{226}(n, m, k) = \begin{cases}1&\text{if n+m-k+m=0 and m=0} ,\ \\0&\text{if n+m-k+m=0 and m>0} ,\ \\\frac{m {\binom{k}{m}} {\binom{- 2 k + 4 m + 2 n}{- k + m + n}}}{- k + 2 m + n} \end{cases} $$