My high school curriculum here in New Zealand seemed to just skip out on this aspect of maths. I'm trying to get a better foundation in this area, and I've been looking through the libraries at university and on the internet. However, I'm not sure which branch of maths sigma notation falls into? Is it algebra? Any help would be great, cause I'm struggling looking up this specific topic in larger maths textbooks.
P.S. I don't think I got the tags correct..