Here is a clever display of the prime factorisation of the numbers 1-200 on a sweater, from knitter Sondra Eklund.

Each prime is represented (as a square) by its own colour, and luckily there’s an infinite number of both. Composites are represented by squares composed of collections of smaller squares or rectangles of appropriate colours.

She has arranged the natural numbers in columns of width ten. Interesting geometric and visual patterns emerge, and on the other side she’s knitted a version with eight to a column, which makes it easier to work in Octal.

As Sondra says, “One of the cool things about this sweater is that it works in any language and on any planet!!!”

Thanks to Ivars Peterson (on Twitter at @mathtourist) for the pointer.

On a similar theme we have Counting Pane http://www.woollythoughts.com/afghans/pane.html. The original was acquired by the London Science Museum. You can buy a pattern to knit your own.

see http://www.scs.illinois.edu/~mainzv/exhibitmath/exhibit/felkel.htm

I co-curated the exhibit of old math books from the UIUC Rare Book Room collection back in 2000, in association with our Millenial Number Theory Conference. This old prime table indicated the smallest prime for odd integers up to about 144,000 using a basically unreadable scheme of letters. The linked picture is of the frontispiece and is charming in its own way.

Thanks to Colin Wright, I found out that you can buy your own prime factorisation jumper, or t-shirt, or tank top from John Graham-Cumming.