More from Chalkdust
Easy to state, hard to prove: The Collatz conjecture
90 years later, we're still unable to prove this surprisingly simple statement
Spam calls and number blocking
Michael Wendl really wants those spammers to stop calling him
Cryptic crossnumber (including hints)
Looking for a challenge? Try our cryptic crossnumber—with hints and tips so anyone can have a go!
In conversation with Christina Pagel
Ellen Jolley asks for (independent) Sage advice
Review of Elastic Numbers
We have a go at the puzzles in Daniel Griller's new book
Man vs Maths
A review of Timothy Revell's new book, describing the hidden mathematics behind our world