# Math Help - Rep unit problem

1. ## Rep unit problem

Just doing a little studying for finals. Can someone help me prove that a rep unit cannot be expressed as the sum of the squares of two natural numbers

2. Originally Posted by MichaelG
Just doing a little studying for finals. Can someone help me prove that a rep unit cannot be expressed as the sum of the squares of two natural numbers
Hint: a repunit is congruent to 3 mod 4.