Number theory

This article explains how credit card numbers are defined and the check digit serves to verify their accuracy.

Tom writes about expressing numbers as the sums of three squares.

An account of methods for finding whether or not a number can be written as the sum of two or more squares or as the sum of two or more cubes.

Peter Zimmerman, a Year 13 student at Mill Hill County High School in Barnet, London wrote this account of modulus arithmetic.