# What is the term for a factorial type operation, but with summation instead of products? [duplicate]

(Pardon if this seems a bit beginner, this is my first post in math – trying to improve my knowledge while tackling Project Euler problems)

I’m aware of Sigma notation, but is there a function/name for e.g.

similar to which uses multiplication?

Edit: I found what I was looking for, but is there a name for this type of summation?

is the $n$th triangular number. This picture demonstrates the reasoning for the name:
$\hskip1.7in$