#mathsonamug #maths pic.twitter.com/wSbBxEd9bm

— Dr. Sean (@seanelvidge) January 18, 2016

I saw someone solving a Sudoku on the train this morning, which made again think about the minimum number of ‘clues’ required to solve a puzzle. It has been proven that you need at least 17 clues to have a unique, solvable, solution.