Actually Fermat himself gave a proof that there were no solutions for
x^4+y^4=z^4
Euler adapted this and proved there were no solutions for
X^3+y^3=z^3
The case n=4 also proves n=8, 12, 16, 20 etc and
the case n=3 also proves n = 6, 9, 12, 15 etc
This rapidly narrowed down the problem - To prove FLT for all n, one has to prove it only for all prime values of n.
(Cases up to n=7 had been proved since a long time)
didn't know this. thanks




Grigori Y Perelman

