There are 81 mitred squares. Each square is constructed by picking up stitches from previous squares.
It is worked in one piece but the maximum number of stitches on the needles, at any time, is 48.
Any yarn can be used. The example shown used DK yarn and measures about 112 cm (45”) square.
Equal amounts of nine different colours are needed. The pattern includes instructions for increasing the size of the afghan.
In the summer of 2015, Alex Bellos and Edmund Harriss published a mathematical colouring book. Some of the designs were similar to afghans we have previously made but their Sudoku design caught our eye, as did a comment by Alex saying he would like to see it as a quilt.
We had always avoided making a conventional Sudoku design, substituting colours for numbers, because a 9 by 9 grid seemed rather uninteresting, Alex and Edmund used a grid where three solutions had been superimposed. Their design used a square inside a square inside a square. We used their numbers but changed the squares to L-shapes for ease of construction for knitters.
This solution has some combinations of colours that are repeated. We then went on to make a crochet versionwith 81 unique squares.