MathDB
An array

Source: Indian RMO 2001 Problem 4

October 27, 2005
linear algebramatrix

Problem Statement

Consider an n×nn \times n array of numbers aija_{ij} (standard notation). Suppose each row consists of the nn numbers 1,2,n1,2,\ldots n in some order and aij=ajia_{ij} = a_{ji} for i,j=1,2,ni , j = 1,2, \ldots n. If nn is odd, prove that the numbers a11,a22,anna_{11}, a_{22} , \ldots a_{nn} are 1,2,3,n1,2,3, \ldots n in some order.