foo, bar

\[\definecolor{b}{RGB}{100,50,255} \definecolor{r}{RGB}{0,0,0} \color{b}\sum\]

Sigma: Denotes repeated addition of something. Sigma comes in two major varieties:

\[ \color{b} \sum_{i=1}^{4} 2\times i \color{r} = 2\times 1 + 2\times 2 + 2\times 3 + 2\times 4 \]


\[ \color{b} \sum_{m\in S} m \]

where \(S\) is any set.

Pi: Like Sigma, but describes repeated multiplication rather than addition.

\[ \color{b} \prod_{i=1}^{4} i \color{r} = 1\times 2\times 3\times 4\]

Comes in the same flavors as Sigma.