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'Wallpaper Sudoku' printed from http://nrich.maths.org/
Produced by Henry Kwok
Rules of "Wallpaper Sudoku"
The puzzle forms repeating patterns of numbers. Hence it is
called "Wallpaper Sudoku".
- All the numbers in the top right box are exactly the same in
values and positions as those in the centre box and bottom left
- The numbers in the top middle box match to those in the middle
left box and bottom right box in values and positions.
- Finally, the numbers in the top left box match in values and
positions those in the middle right box and bottom middle box.
The remaining rules are as in a "standard" Sudoku, and the
object of the puzzle is to fill in the whole 9x9 grid with numbers
1 through 9 so that each horizontal line, each vertical line, and
each of the nine 3x3 squares must contain all the nine different
numbers 1 through 9.
Due to the additional rule of repeating patterns, this puzzle
needs only 9 starters.