Summation

The value of $\Sigma_{i=0}^{\infty} \Sigma_{j=1}^{\infty} 2^{-i} 3^{-j}$ is __________. (Answer in integer)

For a given data set {x1, x2, ..., xn}, where n = 100, it is known that $\frac{1}{2000} \sum_{i=1}^{n} \sum_{j=1}^{n} (x_i - x_j)^2 = 99$ Let us denote $\bar{x} = \frac{1}{n} \sum_...