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Binary Primes (Posted on 2004-02-18)

How many primes, written in usual base 10, have digits that are alternating 1s and 0s, beginning and ending with one?

For example (not necessarily prime):
1, 101, 10101, ...

See The Solution Submitted by Aaron

Rating: 3.5000 (2 votes)

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First thought

| Comment 1 of 13

Past 101, none of them can be prime if they have an even number of 1's, since these are all divisible by 101.

Posted by Brian Wainscott on 2004-02-18 14:20:32

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