Thirty-six squares - one in the first colour, two in the second, three in the third, etc. Adding these numbers together gives the sequence of Triangular Numbers. When you get to 8 the whole shape forms a 6 x 6 square - a Square Number and a Triangular Number coincide.
If you were to keep going, when would this happen again? See our Data Log afghan to find out.
One photo shows the squares spiralling from the centre; in the other they spiral inwards.
Buy using the link at the top of this page
or in 12 Pillows of Wisdom (a PDF book of 12 cushion patterns)