Holy crap, I think I just got it.
Edit: I did not.
This is for contrapositive, which seems more promising.
I have 2^n -1 = p (some prime)
so... 2^n = p+1 (some even)
now, if only log[2](p+1) was something easy and neat.
And I apologize for not showing my work, but most (nearly all) of it has been erased at this point, and it all was deadends. Thanks for your help guys. I'll let you know if/when I get an answer. Or you could put me at peace before that.
Good ol' induction... I didn't try that before. But I took what you started and didn't really end up anywhere... just like everything else I've tried =( Thanks for the thought though.
*sigh* honestly I can't think of a way to factor it =(
I've been up all night and I can't really think straight anymore. I'm not sure that would help anyway though.
Unfortunately I have to prove it for every perfect square, and there are a lot of them.
I feel like I've tried everything. The last thing I tried was contrapositive : If (2^n)-1 is prime, then n is not a perfect square. No dice... at least for me.
Prove that if n is a perfect square, then (2^n) -1 is not prime.
All I can get is that 2^n is some even number. I can't work in the perfect square part.