It seems that there exists no integer k such that 2^k+1 is divisible by a positive integer n, if and only if n is of the form u(8x-1) (where u and x are also both positive integers).(adsbygoogle = window.adsbygoogle || []).push({});

How could this be proved/disproved?

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# 2^k+1 never divisible by u(8x-1) in integers

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