I don't think the $ signs work as math delimiters. I would be nice if they did.
That looks like a simple continued fraction ("simple" is a technical term meaning the numerators are all 1).

I could go on for hours about continued fractions. The way we expand a regular fraction as a continued fraction is essentially Euclid's algorithm for the GCD:

So we have a=2, b=1, c=2, a product
abc=4