I am working on algorithm called as Simultaneous multiple exponentiation, I need to understand the mathematical meaning, like from $j=0$ to $k-1$, how, we calculate the value for $G_i$? What does the mathematical expression mean?
$For\space\ i\space\ = 1 \space\ to\space\ (2^k-1):G_i\leftarrow\prod_{j=0}^{k-1}g_j^{i_j}\space \text{where} \space i=(i_{k-1}\cdots i_0)_2$
Thanks in advance.