Can you use this ancient Greek method to identify prime numbers? Clicking on a number will cycle through the colours; right-clicking will cycle through in reverse order.
The method works by excluding known multiples - remove (by colouring) the multiples of 2, 3, 4, etc., until there are no multiples left. The remaining, uncoloured, squares contain prime numbers.
Starting at the top left, move to the next uncoloured square and colour
the squares containing multiples of the number in the square (but not the
number itself). Repeat until there are no further uncoloured squares.
If you would like to see an implementation of this in Python,