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Repunits and bases (
Posted on 20130724
)
11
_{2}
=3 and 111
_{3}
=13 are prime. However, 1111
_{4}
=85=5*17 and 11111
_{5}
=781=11*71 are not prime. What is the least number n>3 such that the repunit consisting of n 1's in base n is prime?
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Submitted by
Math Man
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re(3): Answer: for any composite, odd or even
Comment 6 of 6 
(In reply to
re(2): Answer: for any composite, odd or even
by Ady TZIDON)
Oh. Now that it has been pointed out, it is both clever and obvious.
Thanks, Ady!
Posted by
Steve Herman
on 20130725 09:31:14
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