1

I came across the following question which asked

Prove that $$\int_{0}^{1} \prod_{k=1}^{\infty} (1-x^k)=\frac{4\pi\sqrt{3}\sinh{\frac{\pi\sqrt{23}}{3}}}{{\sqrt{23}\cosh{\frac{\pi\sqrt{23}}{2}}}}$$

Note: This is the one of the first integrals I have seen like this. I have been looking up other questions (similar to mine) and am still unable to figure out a method to try.

Attempt: I first examined different cases for $k$ and I am able to compute those integrals fine, since they are just polynomials when expanded.

However, I am still stuck with where to begin.

$$\int_{0}^{1} \prod_{k=1}^{\infty} (1-x^k)=(1-x)(1-x^2)(1-x^3) \cdots (1-x^n) \cdots$$

If I were to factor a $-1$ from each term I can see that each term, after the first, contains a factor of $(x-1)$ which might help with some kind of substitution, but that is about as far as I got.

If someone could please offer a hint that will help me get going with this problem.

Thank you.

Joe
  • 955
  • 1
    I am pretty sure this is a duplicate, I remember a Marco Cantarini's answer exploiting the Euler pentagonal number theorem to prove such a claim. – Jack D'Aurizio Aug 19 '16 at 22:23

0 Answers0