What does the notation in the red box mean?
$$\Huge e^{\displaystyle \large \sum_{k=0}^n \bbox[2px,border:2px solid red]{\color{black}
{ {n \choose k}}}~\omega^k}$$
[Math] Meaning of notation with two letters inside of parentheses [binomial coefficient]
math-historynotation
Related Solutions
The usual meaning is "strongly included": $A\subset\subset B$ when $\overline A$ compact and $\overline A\subset B$.
In section 2, the paper gives this definition:
Best Answer
$n\choose{k}$ is a 'binomial coefficient'. Sometimes read '$n$ choose $k$. It represents the number of ways of choosing $k$ items from $n$ distinct items where the order of choice is unimportant.
The value is ${{n}\choose {k}}=\frac{n!}{k!(n-k)!}$
$n$ and $k$ are nonnegative integers with $k\le n$.