$$U_{77}(x, y) = \frac{x^{2} - 2 x - \sqrt{x^{4} - 4 x^{3} + 6 x^{2} - 4 x - 4 y + 1} + 1}{2 y}$$

$$T_{77}(n, m, k) = \frac{k {\binom{k + 2 m - 1}{m}} {\binom{2 k + 4 m + n - 1}{n}}}{k + m}$$