$$U_{1301}(x, y) = \frac{\left(- 2 x \left(y + 1\right)^{2} - \sqrt{- 4 x \left(y + 1\right)^{2} + 1} + 1\right)^{2}}{4 x^{4} \left(y + 1\right)^{6}}$$

$$T_{1301}(n, m, k) = \frac{2 k {\binom{2 k + 2 n}{m}} {\binom{4 k + 2 n}{n}}}{2 k + n}$$