Re: [math-fun] x^n + y^n = z^n + w^n

Was the diophantine x^4+y^4=z^4+w^4 not the subject ofd a paper by the (young) Dyer in ? J/ Lond Math Soc in the aerly 50's while still at school? van der Pol gave a pretty combinatorial proof of the Jacobi 4-ic identity for null thetas. It extends to full thetas, yielding the above identity. Whether this can be used for the diophantine equation, I doubt. John McKay .