N is a positive integer such that each of 3*N + 1 and 4*N + 1 is a perfect square.

Is N always divisible by 56?

If so, prove it. Otherwise, give a counterexample.

(In reply to A start by Jer)

Try mod7.      a must be either 0 mod 7 or +/-3 mod7.

I did , advanced a little, but still did not prove the thing.

Maybe you will... 

 

Posted by Ady TZIDON on 2010-04-02 04:26:48