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Old 2012-10-27, 19:14   #4
Batalov
 
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"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

22·3·7·109 Posts
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For even values of n (and not coprime a,b), indeed, you can arrive to some convenient cancellations (a+b will have to be 2*gcd(a,b)n, where n will be a power of two) and get an extended Generalized Fermat in disguise.
E.g. (6^4+26^4)/(6+26) is xGF'(3,13,4).
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