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IMO 2016 — Complete Shortlist Question 26

IMO Shortlist · IMO 2016 — Complete Shortlist

Question 26

Let $\tau(n)$ be the number of positive divisors of $n$. Let $\tau_{1}(n)$ be the number of positive divisors of $n$ which have remainders 1 when divided by 3 . Find all possible integral values of the fraction $\frac{\tau(10 n)}{\tau_{1}(10 n)}$.