arithmetic - Factorial, but with addition

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.

Answer

It is called the $n$th triangle number and it can be written as $\binom{n+1}2$, as a binomial coefficient.