Is there a Sum Factorial?

Question

I am curious if there is any addition factorial.

Obviously,

$$x! = \prod_{n=1}^x n$$

but what I want is a shorthand way of writing:

$$\sum_{n=1}^x n$$

So is there such a thing? and if so, what is it?

Answer 1

$$ \sum_{k=1}^n k=\frac{n(n+1)}{2}\quad\mbox{or}\quad\sum_{n=1}^x n=\frac{x(x+1)}{2} $$

Answer 2

$\displaystyle\sum_{n=1}^x n$ can be shown to be equal to $\dbinom{x+1}2=\dfrac{(x+1)x}{2}$. I doubt that there's any standard notation designed for precisely that sum.