MathDB
Largest n with a strange condition

Source: Romania JBMO TST 2022 Day 2 Problem 2

May 15, 2022
number theoryRomanian TSTJBMO TST

Problem Statement

Find the largest positive integer nn such that the following is true: There exists nn distinct positive integers x1, x2,,xnx_1,~x_2,\dots,x_n such that whatever the numbers a1, a2,,an{1,0,1}a_1,~a_2,\dots,a_n\in\left\{-1,0,1\right\} are, not all null, the number n3n^3 do not divide k=1nakxk\sum_{k=1}^n a_kx_k.