It is difficult to fit the Fibonacci Sequence on to something as small as a toilet roll cover. This one shows the terms 1, 1, 2, 3, 5, 8, 13 in garter ridges.

You will need about 40 metres/yards DK in each colour.

The ebook contains patterns for eleven knit and crochet toilet roll covers based on mathematical concepts. It also has a section that will help you to design your own covers.

The patterns are not available individually but if you want just one I can supply it in return for a small donation to my favourite charity.