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#656, July 26 - August 1, 2025:
The Weekly 'Unsolvable' Sudoku Puzzle

by Andrew Stuart
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).

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.
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Supporter Members have access to all these puzzles going back to number 1.

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Wednesday 30-Jul-2025

... by: Serban

# 656 E3=4 Basics to 24

1. Box 4 ABC456 n=3 e=6 Nc=20 Ns=2 => B4=4 & [ B5=8 OR A4=9 ] solve

2. Box 5 DEF456 n=3 e=6 Nc=26 Ns=25 => F6=8 & E5=9 solve

3. Box 6 GHJ456 n=3 e=6 Nc=20 Ns=9 => J4=2 solve

Sunday 27-Jul-2025

... by: Dieter

#656 - initially populated cells: 23 = 28,4%
No solver used.
basics: E3=4
populated cells: 24 = 29,6%
Strategy: Numbers 4,1,3,5,6 occur most frequently, combine two cells.
combinations of H5 = (4,5,6,7) and H7 = (2,5,9)
3 matrices remain after basic checks: (H5/H7) = (6/2), (7/2) and (7/9)
(H5/H7) =(7/2) solves with (H6=5 & F5=4)

Review:
F5=4 & H5=7 solve.

Saturday 26-Jul-2025

... by: Frans Goosens

#656

Combination 2-digits cells

A9=7 No solution, Undo calculation
A9=9 No solution, Undo calculation
C5=4 Wrong, Undo calculation
C5=5 ( A6=2 ) Solved,

Total solving time is : 40 sec.
Number of logical steps is : 4789

Saturday 26-Jul-2025

... by: Yves

B5=F6=8 Solve

Saturday 26-Jul-2025

... by: Serban

# 656 Basics to 24

1. Number 2 n=3 e=6 N=32 Nc=77 Ns=15 => C1=2 solve

2. Number 3 n=3 e=6 N=25 Nc=34 Ns=15 => B3=J8=3 solve

3. Number 9 n=2 e=7 N=28 Nc=32 Ns=16 => A4=F8=9 OR H9=9 solve
Page created on 03-May-2011, last modified on 30-May-2024.
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