Show that there exist infinitely many squarefree positive integers that divide . (An integer is squarefree if it contains no factors of the form , .)
Solution
Firstly, note that . Therefore, . Suppose we have chosen distinct primes such that , where the exponent of is when . Then
This shows satisfies the requirement.
By Zsigmondy's theorem, there exists a prime dividing but not . This shows is different from . Therefore, we have
By induction, we can find an infinite sequence of distinct primes such that satisfies the requirement for any . So we are done.
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