P.S. Correction re: 2*gcd(). Not always 2, of course. 2 will frequent, because there are very many prime xGF'(a,b,4) (=(a^4+b^4)/2) with odd a and odd b. Tons. When a+b is 2^{x}, you can finish the counterexample by multiplying a and b by 2^{x1} or similar. Ugh, I need some coffee.
Last fiddled with by Batalov on 20121027 at 19:33
