Place numbers from 1-N in the grid so that each numbers appears exactly once in every row, column and main diagonal. One cell remain empty in each of those. The numbers around the grid show the sum of all the numbers before the empty cell from the given direction in the given row, column or main diagonal.
(Rules and example (N=4) from WPC 2018 IB)
- Untouchable: Furthermore, the same numbers may not touch diagonally.
History of the puzzle
Appeared on WPC 2018/Round 12, an "innovatives" round. The puzzle was written by František Luskač (Czech Rep.). The name is in reference to Doppelblock, sometimes named Double Block from its literal translation of German.