Representations of Integers as Sums of Squares

During the academic year 1980-1981 I was teaching at the Technion-the Israeli Institute of Technology-in Haifa. The audience was small, but con­ sisted of particularly gifted and eager listeners; unfortunately, their back­ ground varied widely. What could one offer such an audience, so as to do justice to all of them? I decided to discuss representations of natural integers as sums of squares, sta...