#717, September 26 - October 2, 2026:
The Weekly 'Unsolvable' Sudoku Puzzle
by Richard Kröger, guest compiler
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WARNING: This is the Weekly 'Unsolvable' Sudoku, rated above 'Extreme'.
This is currently unsolvable by my solver, except perhaps with trial and error strategies.
Using the solver will not help you. (much).
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Changes March 2026
Due to the introduction of
Forcing Nets many Weekly Unsolvable puzzles can now
be solved. I have flagged all the Sudoku ones which are solvable. I am struggling to make any new ones so we'll
have to see if the Weekly can continue. The point of the Weekly was to provoke discussion and new ideas, so
that is progress. But my solution is unlikely to be optimal so alternatives are welcome.
Archive
Each week a new 'unsolvable' will be published and the previous will be accessible here from this archive section.
If you like very tough puzzles, these are for you.
Share and Enjoy
Supporter Members have access to all these puzzles going back to number 1.
Discussion...
Post an idea here...
... by: Norman Powell
AS's Solver only finds Hidden Singles 8H1 & 4H7.
My Solver:
Confined to Box: Value 3 confined to Column 5 and Box 2, eliminate 3G5 & 3J5.
[AS's Solver should have picked this up as a Pointing Pair?]
Alternative Inference Chain [Placed before Forcing Networks in my method order]:
3J1 has weak links to both ends of chain, which would cause a contradiction so eliminate.
Chain: -1H3+1H4-2H4+2J4-7J4+7J5-5J5+5J1-
Grouped X-Cycles [Placed after AIC in my methods order]:
1A3 & 1B3 has weak links to both ends of the following chain: which would cause a contradiction so eliminate:
-1H3+1H4-1E4+1[E2 E3]-1D1+1[A1 B1]-
Forcing Network Pass 1: Finds nothing until testing 9C3 for being ON, when it finds the solution:
547932168186574293329681547718346952693125784452897316265413879871269435934758621
[This is equivalent to AS's Bowman's Bingo]
I am not sure why AS's Solver did not proceed further?
