ton wrote:I think minimum numbers are about "floor(n^2 / 4) - (h - 1)(w - 1)".
Are "h" and "w" from your formula height and width of the box? (For 20 x 20 Sudoku h=4, w=5, n=20.) How did you get this formula? It gives 16 - minimal number of clues for 9 x 9 Sudoku. Almost right answer.
Serg
