posted by Sean .
Can someone use mod to prove that 10^(3n + 1) cannot be represented as the sum of two cubes.
And make it very detailed please.
I know your are suffering Sean, so i'll tell u. USE base 7. Cubes mod 7 cant have a residue of 3 or 4. 10 ^ 3n + 1 dose and only has a residue of 10 ^ 3n +1. So there u go sean yu.