IMO Shortlist 1978 problem 8


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2. travnja 2012.
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Let S be the set of all the odd positive integers that are not multiples of 5 and that are less than 30m, m being an arbitrary positive integer. What is the smallest integer k such that in any subset of k integers from S there must be two different integers, one of which divides the other?
Izvor: Međunarodna matematička olimpijada, shortlist 1978