Intro to writing C-extension for Python
danfm.ca
Also has some nice numpy specific stuff for scientific code
danfm.ca
that said, learning the intricacies of an extension - and all of the stuff you have to do under the hood like registering handlers, reference counting, cleanup, etc - is a valuable experience.
but once you got that done i just recommend you use code generators. it's also a lot easier to maintain.
Learning the meaning of math symbols is actually easier than learning a new programming language, or some cumbersome API. (I assume that you have no problem picking up a new language, as this article is directed to people who have learned at least two quite different languages: C and Python.)
So if it's just a formula, what would be math? Math would be describing exactly what problem is solved by this function, proving that the formula's result will indeed have the desired properties, and checking all edge cases and interesting special cases of that function. And on top of all this, math would analyze the effects of floating point inaccuracies on the result.
So this article doesn't really contain math. It contains just a formula, which shouldn't be any more intimidating than the corresponding C function.