Studing the Gordon file I found somes rules that I submit to the autors o 17 clues

Beware the rules does't give valid solutions they eliminate bad

The grid must respect the rules but a grid respecting the rules is not necessary a valid sudoku.

I get the rules only with observations not with math computing so they can be bad!

If you have other technics of if a rule is bad said it

The rules are ONLY for 17 clies!!!!

A Box2 is a box with two clues

2 Row4 are 2 rows with each 4 clues

2 Digit4 means that you have two digits present 4 times

A set is a row, a column or a box of 9 cells.

A empty set is a row, column or box with no clue

1-You cannot have four empty row or col.

2-There only one combination with 3-2 empty rows cols.

3-Maximum 2 empty box

4-2 Empty boxes are exceptional but possible

5-If you have two empty boxes you cannot have empty row or col

6-The maximum of clues for a row, a column or a box is 5

7-You never have the maximum of two set at the same time.

8- If you have 5 clues in a box you can have only one empty box

9- If you don’t have a box with only one clues You have 1 or two empty box

10- If you don’t have a box with only one clues Dont have box with 4 or 5 clues

11- You can have only two boxes with 4 clues

12- If you have a Box4 you cannot have 5 boxes

13- If you have two 4 boxes you have at less 2 box2

14- If you have only 1 Box1 and no empty box the 8 other boxes are 8 box2

15- Maxi 4 box3

16- You never have the same digit 5 times

17- You don’t have more than 2 digit4

18- You have 5 digit1 you have 3 digit3

19- 18 is the only problem where you don’t have Digit2

20- You always have at 8 or 9 differents digits (Only 7 differents digit is ompossible)

Papy

It's the fordt set of rules I found others but I prefer to verify them

Have a lot of fun