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
box.
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.