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.