Constraint of Sudoku problem

[kan]

The above constraint wants to describe what condition in the Sudoku problem?

I think the constraint here is that the numbers [MATH]1[/MATH] to [MATH]9[/MATH] appear exactly once on each square [MATH]3[/MATH]x[MATH]3[/MATH], but I think there is a small mistake in the constraint. I'm not sure either

Hope everyone helps. Thanks for very much!

 

[JeffM]

I am not sure I can help, but I suspect that no one can help until you say what x and n are. You have given a formula with nothing defined. Moreover, there are nine 3X3 segments, and this constraint apparently applies to only four elements.