Every vertex has an even degree, yet the picture cannot be drawn with a single stroke.
More from Chalkdust
Issue 21
Sudoku, potatoes and crossnumber's biggest secrets finally revealed in our spring 2025 issue. Plus all your favourite columns!
Chalkdust issue 20 – Coming 8 November
Pre-order your copy of our 9½-year anniversary issue now!
In conversation with Jens Marklof
Bethany Clarke and Enric Solé-Farré chat to the professor and new president of the London Mathematical Society about academia, access and awards
Review: Mathematical T-shirt
A summer essential or an embarrassment risk on the streets of Ibiza?
Crossnumber winners, issue 04
Are you a winner?
Do you have too many or too few friends?
Do we have a natural limitation on the number of friends that we have?