In 1779, the Swiss mathematician Leonhard Euler posed a puzzle that has since become famous: Six army regiments each have six officers of six different ranks. Can the 36 officers be arranged in a 6-by ...

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory. She reports on topics from maths and history to society and animals. Katie has a PhD in maths, ...

If you purchase an independently reviewed product or service through a link on our website, Rolling Stone may receive an affiliate commission. Few things are as meditative or calming as sitting down ...