How many incongruent primitive roots does 13 have?












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How many incongruent primitive roots does 13 have?:



So far I know that phi(phi(13)) = phi(12) = 4, so there would be 4 primitive roots. And a RRS mod 13 is {1,2,3,...,12}. But I'm not sure where to go from here to find the incongruent primitive roots. Any help would be appreciated!










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    $13$ is small, you could brute-force it. But if you have found one primitive root, do you know how to get the others from it?
    $endgroup$
    – Daniel Fischer
    Feb 4 '16 at 0:52










  • $begingroup$
    The only candidates are the quadratic non-residues. That cuts down on the work. There are further shortcuts, which are not worth using here.
    $endgroup$
    – André Nicolas
    Feb 4 '16 at 1:43
















1












$begingroup$


How many incongruent primitive roots does 13 have?:



So far I know that phi(phi(13)) = phi(12) = 4, so there would be 4 primitive roots. And a RRS mod 13 is {1,2,3,...,12}. But I'm not sure where to go from here to find the incongruent primitive roots. Any help would be appreciated!










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    $13$ is small, you could brute-force it. But if you have found one primitive root, do you know how to get the others from it?
    $endgroup$
    – Daniel Fischer
    Feb 4 '16 at 0:52










  • $begingroup$
    The only candidates are the quadratic non-residues. That cuts down on the work. There are further shortcuts, which are not worth using here.
    $endgroup$
    – André Nicolas
    Feb 4 '16 at 1:43














1












1








1


1



$begingroup$


How many incongruent primitive roots does 13 have?:



So far I know that phi(phi(13)) = phi(12) = 4, so there would be 4 primitive roots. And a RRS mod 13 is {1,2,3,...,12}. But I'm not sure where to go from here to find the incongruent primitive roots. Any help would be appreciated!










share|cite|improve this question









$endgroup$




How many incongruent primitive roots does 13 have?:



So far I know that phi(phi(13)) = phi(12) = 4, so there would be 4 primitive roots. And a RRS mod 13 is {1,2,3,...,12}. But I'm not sure where to go from here to find the incongruent primitive roots. Any help would be appreciated!







number-theory






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asked Feb 4 '16 at 0:49









whatarethosewhatarethose

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  • 2




    $begingroup$
    $13$ is small, you could brute-force it. But if you have found one primitive root, do you know how to get the others from it?
    $endgroup$
    – Daniel Fischer
    Feb 4 '16 at 0:52










  • $begingroup$
    The only candidates are the quadratic non-residues. That cuts down on the work. There are further shortcuts, which are not worth using here.
    $endgroup$
    – André Nicolas
    Feb 4 '16 at 1:43














  • 2




    $begingroup$
    $13$ is small, you could brute-force it. But if you have found one primitive root, do you know how to get the others from it?
    $endgroup$
    – Daniel Fischer
    Feb 4 '16 at 0:52










  • $begingroup$
    The only candidates are the quadratic non-residues. That cuts down on the work. There are further shortcuts, which are not worth using here.
    $endgroup$
    – André Nicolas
    Feb 4 '16 at 1:43








2




2




$begingroup$
$13$ is small, you could brute-force it. But if you have found one primitive root, do you know how to get the others from it?
$endgroup$
– Daniel Fischer
Feb 4 '16 at 0:52




$begingroup$
$13$ is small, you could brute-force it. But if you have found one primitive root, do you know how to get the others from it?
$endgroup$
– Daniel Fischer
Feb 4 '16 at 0:52












$begingroup$
The only candidates are the quadratic non-residues. That cuts down on the work. There are further shortcuts, which are not worth using here.
$endgroup$
– André Nicolas
Feb 4 '16 at 1:43




$begingroup$
The only candidates are the quadratic non-residues. That cuts down on the work. There are further shortcuts, which are not worth using here.
$endgroup$
– André Nicolas
Feb 4 '16 at 1:43










1 Answer
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The four incongruent primitive roots of $13$ are $g^k$ for $g$ a primitive root and $k$ coprime with $12$, that is, $k=1,5,7,11$. They can also be given by $pm g, pm g^5$ because $g^6=-1$.






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    $begingroup$

    The four incongruent primitive roots of $13$ are $g^k$ for $g$ a primitive root and $k$ coprime with $12$, that is, $k=1,5,7,11$. They can also be given by $pm g, pm g^5$ because $g^6=-1$.






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      0












      $begingroup$

      The four incongruent primitive roots of $13$ are $g^k$ for $g$ a primitive root and $k$ coprime with $12$, that is, $k=1,5,7,11$. They can also be given by $pm g, pm g^5$ because $g^6=-1$.






      share|cite|improve this answer











      $endgroup$
















        0












        0








        0





        $begingroup$

        The four incongruent primitive roots of $13$ are $g^k$ for $g$ a primitive root and $k$ coprime with $12$, that is, $k=1,5,7,11$. They can also be given by $pm g, pm g^5$ because $g^6=-1$.






        share|cite|improve this answer











        $endgroup$



        The four incongruent primitive roots of $13$ are $g^k$ for $g$ a primitive root and $k$ coprime with $12$, that is, $k=1,5,7,11$. They can also be given by $pm g, pm g^5$ because $g^6=-1$.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Dec 26 '18 at 10:23

























        answered Feb 4 '16 at 1:12









        lhflhf

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        166k10171400






























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