1.
The sum of the series 1+23(18)+2×53×6(18)2+2×5×83×6×9(18)3+1 + \frac{2}{3}\left(\frac{1}{8}\right) + \frac{2\times5}{3\times6}\left(\frac{1}{8}\right)^2 + \frac{2\times5\times8}{3\times6\times9}\left(\frac{1}{8}\right)^3 + \ldots is