# Factorial, but with addition [duplicate]

Is there a notation for addition form of factorial?

That’s pretty obvious. But I’m wondering what I’d need to use to describe

like the factorial $5!$ way.

EDIT: I know about the formula. I want to know if there’s a short notation.

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