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What is the smallest integer n, greater than 1, such that 1/n (mod 130)  and 1/n (mod 9) are both defined?

 Jul 3, 2021
 #1
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What is the smallest integer n, greater than 1, such that
1n(mod130) and 1n(mod9)

are both defined?

 

There is an invertible modulo 130, if gcd(130,n)=1 (130 and n are relatively prime)
There is an invertible modulo 9, if gcd(9,n)=1  (9 and n are relatively prime)

 

n>1

 

ngcd(130,n)gcd(9,n)2gcd(130,2)=2gcd(9,2)=13gcd(130,3)=1gcd(9,3)=34gcd(130,4)=2gcd(9,4)=15gcd(130,5)=5gcd(9,5)=16gcd(130,6)=2gcd(9,6)=37gcd(130,7)=1gcd(9,7)=1

 

The smallest integer is 7

17(mod130)93 and 17(mod9)4

 

 

laugh

 Jul 4, 2021

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