Stage: 3 Challenge Level: 
Generalising. Number - generally. Mathematical reasoning & proof. Relations. Number theory. Creating expressions/formulae. Reflexive and transitive laws. Visualising. Combinatorics. Patterned numbers.
Published October 1998.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk