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1964 IMO Problems/Problem 1

Revision as of 19:16, 15 July 2009 by Xpmath (talk | contribs) (Created page with '== Problem == (a) Find all positive integers <math>n</math> for which <math>2^n-1</math> is divisible by <math>7</math>. (b) Prove that there is no positive integer <math>n</mat…')
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Problem

(a) Find all positive integers $n$ for which $2^n-1$ is divisible by $7$.

(b) Prove that there is no positive integer $n$ for which $2^n+1$ is divisible by $7$.

Solution

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