## Articles

**C. J. Sangwin**shows us how eighteenth-century mathematician Leonhard Euler solved one of the foremost infinite series problems of his day.

**Paulus Gerdes**takes us on a tour of the mathematical properties of some beautiful designs inspired by the traditional art of Angolan tribespeople.

*Plus*talks to

**Sir Roger Penrose**about all this and more.

**Colin Adams**asks when is a molecule knot a molecule? and what happens if you try to build a knot out of sticks?

**Rachel Thomas**looks at Shannon's life and works.

**Matthew Keeling**describes some of the mathematical developments that have improved our understanding and predictive ability.

**Ian Garbett**discusses radioactive decay.