$$U_{1455}(x, y) = \frac{- \frac{2 x}{1 - y} - \sqrt{- \frac{4 x}{1 - y} + 1} + 1}{2 x^{2} \left(1 - y\right)}$$

$$T_{1455}(n, m, k) = \frac{k {\binom{2 k + 2 n}{n}} {\binom{3 k + m + n - 1}{m}}}{k + n}$$