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, ...

(In reply to Another thought by Brian Wainscott)

Well, only the numbers with prime number of 1's can be considered, the only exception is 10101

Posted by WAyne on 2007-09-30 06:26:58