# Questions tagged [coprime]

Use this tag for questions related to integers such that the only positive integer that divides them is 1.

108 questions
Filter by
Sorted by
Tagged with
2answers
162 views

### How to prove the following expression

Prove that if it takes you 5 minutes to solve any Sudoku puzzle and 14 minutes to solve a word search, you can completely occupy yourself on any flight of 52 minutes or longer provided that you have a ...
1answer
56 views

1answer
63 views

### General formula for the gcd.

It seems there is no closed form for the greatest common divisor of any two given integers. Why is there no such formula? Does the only way to compute the gcd is essentially to recursively apply the ...
4answers
77 views

1answer
59 views

### Relatively prime numbers are prime

The problem is to find all numbers $n$ such that all numbers $k>1$ smaller than $n$ and coprime with $n$ are prime.
0answers
41 views

### Best error term in $\sum_{(n,q)=1}\frac{1}{n}$ (harmonic series with coprimality condition)

It is very well known and not difficult to prove that \$\displaystyle\sum_{\substack{0<n\leq X\\ \\(n,q)=1}}\frac{1}{n}=\left(\log(X)+\gamma+\sum_{p|q}\frac{\log(p)}{p-1}\right)\frac{\phi(q)}{q}+O\...