infinite series
What is 11+11+11+...? How infinite sums challenge our notion of arithmetic. 

What do you get when you add up all the natural numbers 1+2+3+4+ ... ? Not 1/12! We explore a strange result that has been making the rounds recently. 
The number pi can be expressed beautifully in terms of infinite sums. For practical purposes though, these sums are rather disappointing: they converge slowly, so you need to sum a large number of terms to get accurate estimates of pi. Here's a clever way to make them converge faster. 
Two computer geeks claim to have calculated the number pi to 5 trillion digits — on a single desktop and in record time. That's 2.3 trillion digits more than the previous world record held by the Frenchman Fabrice Bellard. 
Mathematics takes to the stage with A disappearing number, a work by Complicite, inspired by the mathematical collaboration of Hardy and Ramanujan. Rachel Thomas went to see the play, and explains some of the maths. You can also read her interview with Victoria Gould about how the show was created.

Victoria Gould has always known she would be an actor, and went straight from studying arts at school to running her own theatre company. But she eventually had to come clean about her guilty secret  she loves maths  and has since managed to combine a career as a research mathematician and teacher with a successful acting career on television and in theatre. She tells Plus why she needs to use
both sides of her brain.

Leonhard Euler was one of the most prolific mathematicians of all time. This year marks the 300th anniversary of his birth. Robin Wilson starts off a four part series on Euler with a look at his life and work.

Infinite series occupy a central and important place in mathematics. C. J. Sangwin shows us how eighteenthcentury mathematician Leonhard Euler solved one of the foremost infinite series problems of his day.
