The first row represents the numbers 1 to 10, the second 11 to 20, and so on. The numbers from 1 to 10 each have a colour. This is at the top of the column. 1 is blue, 2 is yellow, etc. If these numbers divide into the number of a square the colour is shown in the square.
Squares and parallelograms create the illusion of cubes, using three shades.
How many different squares can be made by using two yarns at a time from a choice of ten?A practical use for triangular numbers.