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#686, February 21 - February 27, 2026:
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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Saturday 21-Feb-2026

... by: Dieter

#686 - initially populated cells: 23 = 28,4 %
No solver used, solver = brain.
basics: C9=J5=4; A1=6; C7=9
populated cells: 27 = 33,3 %
Strategy: numbers 4,6,8,1,9 occur most frequently, combine two cells.
combinations of D1 = (1,2,4,5,7) and D4 = (1,5,6,7)
after basic checks 1 matrix left: D1/D4 = 2/1
D1/D4 = 2/1 solves with J4=5

Optimization:
D1=2 & J4=5 solve.

Saturday 21-Feb-2026

... by: Yves

F4=8 or G6=8 or F6=9

Saturday 21-Feb-2026

... by: Serban

# 686 A1=6 C9=J5=4 C7=9 Basics 27

1. F4=8 OR G6=8 solve

2. F6=9 OR G3=9 solve
Page created on 03-May-2011, last modified on 30-May-2024.
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