How do you show that a Fermat number is not prime?

**JRichardson1729** · October 17th 2010, 10:36 AM

I recently happened upon a problem that I cannot make any headway on. Here it is:

Using the factorization of $x^n+1$ when $n\geq 3$ and is odd, show that $2^3^2+1$ is not prime.

I found this video, , that shows this, but, unfortunately, I don't think that it uses the factorization of $x^n+1$ when $n\geq 3$ and is odd and I don't know how to adapt it so that it does (if that is possible at all).

Thank you. All help with this problem is appreciated.

**JRichardson1729** · October 21st 2010, 08:11 AM

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