MathDB
Differences between two consecutive members of s

Source: IMO Longlist 1989, Problem 106

September 18, 2008
floor functionnumber theoryprime numbersalgebra unsolvedalgebra

Problem Statement

For every sequence (x1,x2,,xn) (x_1, x_2, \ldots, x_n) of non-zero natural prime numbers, {1,2,,n} \{1, 2, \ldots, n\} arranged in any order, denote by f(s) f(s) the sum of absolute values of the differences between two consecutive members of s. s. Find the maximum value of f(s) f(s) where s s runs through the set of all such sequences, i.e. for all sequences s s with the given properties.