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Infinitely many numbers of a given form

Source: EGMO 2016 Day 2 Problem 6

April 13, 2016
number theoryEGMODivisorsEGMO 2016

Problem Statement

Let SS be the set of all positive integers nn such that n4n^4 has a divisor in the range n2+1,n2+2,...,n2+2nn^2 +1, n^2 + 2,...,n^2 + 2n. Prove that there are infinitely many elements of SS of each of the forms 7m,7m+1,7m+2,7m+5,7m+67m, 7m+1, 7m+2, 7m+5, 7m+6 and no elements of SS of the form 7m+37m+3 and 7m+47m+4, where mm is an integer.