But even the most dedicated Sudoku-solver might have never spotted this ... A Sudoku is a puzzle involving a 9x9 grid into which the numbers one to nine must be placed. The catch is that each ...

But even the most dedicated Sudoku-solver might have never spotted this ... A Sudoku is a puzzle involving a 9x9 grid into ...

A Sudoku puzzle consists of a 9x9 grid of squares ... and it's up to the solver to figure out how to fill in the rest of the squares to get to that end state. Mathematicians love counting things.