$$U_{1091}(x, y) = \frac{\left(y + 1\right)^{2} \left(- 2 x - \sqrt{1 - 4 x} + 1\right)^{3}}{8 x^{6}}$$

$$T_{1091}(n, m, k) = \frac{3 k {\binom{2 k}{m}} {\binom{6 k + 2 n}{n}}}{3 k + n}$$