the numbers form an arithmetic progression
Source: China TST 1994, problem 2
May 17, 2005
functionratioarithmetic sequencealgebrasystem of equationscombinatorics unsolvedcombinatorics
Problem Statement
An by grid, where every square contains a number, is called an -code if the numbers in every row and column form an arithmetic progression. If it is sufficient to know the numbers in certain squares of an -code to obtain the numbers in the entire grid, call these squares a key.
a.) Find the smallest such that any squares in an code form a key.
b.) Find the smallest such that any squares along the diagonals of an -code form a key.