can arithmetic mean of p squares from a set of (p^2 + 1)/2 be an integer?
Source: 2021 Austrian Federal Competition For Advanced Students, Part 2, p6
June 6, 2021
number theoryPerfect SquarePerfect Squares
Problem Statement
Let be an odd prime number and a set derived from square numbers.
Investigate whether elements can be selected from this set whose arithmetic mean is an integer.(Walther Janous)