Some Square Over The Rainbow
This is one of our earliest designs but still very popular.
It is obvious that it has the seven colours of the rainbow and that it has squares but it also repesents one way of generating square numbers.
Every square number is the sum of odd numbers. The odd numbers here are shown in the L shapes:
1 + 3 + 5 + 7 + 9 + 11 + 13 = 49, which is the square of 7.
This is a very easy design to make, worked entirely in garter stitch. It doesn't have to be worked in rainbow colours. I think it would be very effective with alternating bands of black and white.
I used Aran yarns but the method would work with any yarn. You can adjust the size of the squares to suit your yarn.