perplexus.info :: Numbers : Binary Primes

Home > Numbers

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)

Comments: ( Back to comment list | You must be logged in to post comments.)

Oh god! I read the question wrong.

| Comment 8 of 13 |

There are only 2 prime numbers if you are ALTERNATING 1's and 0's 1 and 101. All others are divisible by 3. (I think I got it straightened out finally.

Posted by Mitch Mullings on 2004-02-22 20:59:37

Please log in:

Login:
Password:
Remember me:

Sign up! \| Forgot password

Search:

Search body:

Forums (1)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (6)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:


perplexus dot info