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remainder upon division, prove equation

Source: Yugoslav TST 1982 P1

May 29, 2021
number theory

Problem Statement

Let p>2p>2 be a prime number. For k=1,2,,p1k=1,2,\ldots,p-1 we denote by aka_k the remainder when kpk^p is divided by p2p^2. Prove that a1+a2++ap1=p3p22.a_1+a_2+\ldots+a_{p-1}=\frac{p^3-p^2}2.