Factorial, but with addition [duplicate]

Is there a notation for addition form of factorial?

5!=5×4×3×2×1

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 nth triangle number and it can be written as \binom{n+1}2, as a binomial coefficient.

Attribution
Source : Link , Question Author : akinuri , Answer Author : endolith

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