In the book [1, p. 54] the authors mention the following identity of Gauss $$\prod_{n\ge 1}(1-x^n)^3=\sum_{r\ge0}(-1)^r(2r+1)x^{r(r+1)/2}$$ and write
Several proof are known for the Gauss identity, and they belong to very different parts of mathematics, such as homological algebra, complex analysis, and hyperbolic geometry.
Question. Where may I find the "homological algebra" proof of the Gauss identity.
Thanks.
[1] Mathematical Omnibus: Thirty Lectures on Classic Mathematics
