Is it possible to arrange on a circle all composite positive integers not exceeding 106, so that no two neighbouring numbers are coprime?
Author: L. Emelyanov
[hide="Tuymaada 2008, Junior League, First Day, Problem 2."]Prove that all composite positive integers not exceeding 106
may be arranged on a circle so that no two neighbouring numbers are coprime. AMCUSA(J)MOUSAMOnumber theoryprime numbersnumber theory unsolved