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
Does this explain why 7 is a factor of n? by broll)
Unfortunately it does not.
In steps 3 and 4 all you really did was introduce variables k and l (the x and y seem irrelevant.)
In steps 5 and 6 you prove that (k+l) is divisible by 7. For instance if n=3, (k+l)=21.

Posted by Jer
on 20100406 10:18:02 