discussion on MathOverflow http://mathoverflow.net/questions/31113/zagiers-one-sentence-proof-of-fermats-theorem http://mathoverflow.net/questions/31113/zagier

discussion on MathOverflow http://mathoverflow.net/questions/31113/zagiers-one-sentence-proof-of-fermats-theorem http://mathoverflow.net/questions/31113/zagiers-one-sentence... they also find a involution based proof that p = x² + 2y² if and only if p = 8k+1 or p = 8k+3 it is possible to turn this existence proof into a constructive proof. as in section 2 of this paper: http://www.math.tugraz.at/~elsholtz/WWW/papers/papers30nathanson-new-address3.pdf http://www.math.tugraz.at/~elsholtz/WWW/papers/papers30natha...