http://mathworld.wolfram.com/Fermat4nPlus1Theorem.html

Jon Perry

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-----Original Message-----

From: Paul Jobling [mailto:Paul.Jobling@...]

Sent: 28 March 2003 15:09

To: 'Adam'; primenumbers@yahoogroups.com

Subject: RE: [PrimeNumbers] Re: 24n+1 is prime

Fermat showed that every prime of the form 4n+1 can be expressed as the sum

of

two squares in exactly one way.

As a prime of the form 24n+1 is 1 mod 3, x^2+y^2 must be 1 mod 3, and that

can

happen if exactly one of them is divisible by 3.

What is the problem here?

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