Not all programmers come from a maths background. In fact, if you're self-taught, chances are you've stumbled on a useful mathematical formula (say, on Wikipedia), except its in formal notation and might as well be Sanskrit. Sometimes you can get lucky and find code snippets, but if you're reading straight from research papers, this isn't always an option. Fortunately, you can translate it, if you have the time.
If you're curious, here's the start of the explanation of sigma (Σ):
Sadly, there isn't an automated way to convert notation to code, but at the very least you can use this to make the process easier.