Every vertex has an even degree, yet the picture cannot be drawn with a single stroke.
More from Chalkdust
Here Come the Numbers
We review the fourth of this year's nominees for the Book of the Year
Prize crossnumber, Issue 08
Win £100 of Maths Gear goodies by solving our famously fiendish crossnumber
David Blackwell and me
Clive Fraser reflects on his interactions with one of the greatest ever Black mathematicians
Christmas conundrum #3
Try our nonograms! And remember, not all puzzles have a unique solution...
A brief history of gravitational waves
The discovery of gravitational waves offers a new way of looking at the universe. Who knows what we will discover?
What’s your favourite number?
Favourite numbers for many are linked to birthdays or anniversaries, but here is our take on the question