Sigma Notation Cheat Sheet

I'm just over a quarter of the way through MST121: Using Mathematics, which I started back in September. My impression is that it's starting to get tougher, but it may just be that my mind has been elsewhere.

One concept with which I found myself to be less confident is Sigma Notation. The principle itself is fairly straightforward (it's kind of like a for loop, if you ask me) but getting actual numbers out of the other side was another matter.

The problem was that I was consistently failing to spot the patterns that indicate that you can substitute in other, hopefully simpler, expressions. So I made a little aide memoire to print out. It covers the three four initial, erm, refactorings that have cropped up, and I figured I may as well share it.