TITLE: Factorial, but with addition
QUESTION [83 upvotes]: Is there a notation for addition form of factorial?
$$5! = 5\times4\times3\times2\times1$$
That's pretty obvious. But I'm wondering what I'd need to use to describe
$$5+4+3+2+1$$
like the factorial $5!$ way.
EDIT: I know about the formula. I want to know if there's a short notation.

REPLY [20 votes]: We should also note that the factorial function has a similar look to it as the sigma summation notation; as
$$\frac{n(n+1)}{2}=1+2+3+...+n=\sum_{k=1}^nk$$
$$n!=1 \cdot 2 \cdot 3 \cdot ... \cdot n=\prod_{k=1}^nk$$