Rules Find the whole set of dominos with numbers 1 to 6 by dividing the grid into orthogonally connected areas with two digits each.
This variation on the standard Domino puzzle featured on the Dutch round of last year’s WPC, there’s some more on Bram’s blog.
There should be two quite different ways to get started on this one.
Maybe Puzzles 
Why is there none of a 4-2 domino can be made? I think you created it wrong somehow?
You might have missed the variant rule? That frame of empty cells along the border of the puzzle can be used by the “dominos”.
Oh? So you can input any number 1-6 to any cells to complete the puzzle? Will it have more than 1 answer?