# I found something, but I'm not sure what it is. Summation Notation

I came across this yesterday when I was looking for equalities between the sums of two summations.
I'm not sure if this is part of a proof or what.

## Answers and Replies

To see how this equality is true, remember that the sum of the first n integers is given by the formula: n(n+1)/2

I'd not come across that before... pretty nice :) Simple yet elegant

Thanks :) I'm 15 and just learned summation notation. I was playing with it for a few hours Saturday and my high school Geometry teacher thought it was pretty neat.