Tuesday, 24 January 2017

elementary number theory - Is every non-square integer a primitive root modulo some odd prime?

This question often comes in my mind when doing exercices in elementary number theory:




Is every non-square integer a primitive root modulo some odd prime?





This would make many exercices much easier. Unfortunately I seem unable to discover anything interesting which may lead to an answer.



It seems likely to me that this is true. If n2(mod3) then it's a primitive root modulo 3. If n2,3(mod5), it's a primitive root modulo 5. If we would continue like this, my guess is that any non-square n will satify at least one of these congruences.



This being difficult, I began considering a simplified question:




Is every non-square integer a quadratic non-residue modulo some prime?





Or equivalently,




If an integer is a square modulo every prime, then is it a square itself?




The second form seems easier to approach, however I still can't find anything helpful.

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