MathDB
Permutation and residues

Source: Baltic Way 2017 Problem 18

November 11, 2017
number theoryabstract algebra

Problem Statement

Let p>3p>3 be a prime and let a1,a2,...,ap12a_1,a_2,...,a_{\frac{p-1}{2}} be a permutation of 1,2,...,p121,2,...,\frac{p-1}{2}. For which pp is it always possible to determine the sequence a1,a2,...,ap12a_1,a_2,...,a_{\frac{p-1}{2}} if it for all i,j{1,2,...,p12}i,j\in\{1,2,...,\frac{p-1}{2}\} with iji\not=j the residue of aiaja_ia_j modulo pp is known?