Apply classic sudoku rules. The clues outside the grid indicate all digits (not necessarily in the given order) which have two even digits as immediate neighbours in the corresponding row or column. If a digit is no clued outside the grid, then its two immediate neighbours in that row or column must not both be even.
Notes:Variants:
- Rows or columns with a dash (-) indicate that there are no digits with two immediate even neighbours in that row or column.
If a row or column is unclued (where no information is given), that row or column can have any number of sandwiched digits, including none at all.