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

  1. #1
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    How do you show that a Fermat number is not prime?

    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, YouTube - the 5th Fermat number is not a prime (german), 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.
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  2. #2
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    Bump.
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