Related to divisibility are 'Greatest Common Divisors'. The greatest
common divisor of two (or more) numbers is defined as: the largest
number that divides those numbers. The Greatest Common Divisor of 10 and
15 - notation GCD(10,15)- for instance is 5.
In the following diagram allows you to display nuber pairs with a chosen
GCD, starting off with showing number pairs with GCD 2.