Number theory · Primes · Congruences · Quadratic residues · Parity

Problem 3, 2024

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RegionalProof

Find all prime numbers \(p\), \(q\) and \(r\) for which the number

\[ p^{\,q+r} + q^{\,p+r} + r^{\,q+p} \]

is the square of an odd natural number.

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Serbian Regional Competition (Okruzno takmicenje) 2024, high school grade I, category A, problem 3. Organized by the Mathematical Society of Serbia (DMS). Source