Limits RegistryPUBLIC RECORD
Limits RegistryGary McGuire, Bastian Tugemann and Gilles Civario of University College Dublin announced in January 2012, and published in Experimental Mathematics in 2014, an exhaustive computer search proving that no 16-clue Sudoku has a unique solution. The search checked every essentially different completed grid for 16-clue unavoidable-set hitting sets, run on supercomputers of the Irish Centre for High-End Computing (ICHEC).
The question, scope, and sources behind this Registry record.
Gary McGuire, Bastian Tugemann and Gilles Civario of University College Dublin announced in January 2012, and published in Experimental Mathematics in 2014, an exhaustive computer search proving that no 16-clue Sudoku has a unique solution. The search checked every essentially different completed grid for 16-clue unavoidable-set hitting sets, run on supercomputers of the Irish Centre for High-End Computing (ICHEC).
No proper 9x9 Sudoku puzzle (one with a unique solution) has 16 or fewer clues, and puzzles with 17 clues exist; hence the minimum is 17.
Change a parameter to stress-test whether a proposed result is still inside the published specification. This is an audit aid, not a proof checker.
This record has no editable parameters. Read the formal question and assumptions before challenging it.
Current frontiers derived from accepted Claims.
An observed or demonstrated result; no opposing bound is implied.
The frontier is not sacred
Most progress starts with a disagreement that survives contact with evidence. If you can push the known lower bound up or pull the upper bound down, show us the work.
≥ when you have shown that at least this value is achievable.≤ when you have shown that anything above this value is impossible.No vibes. State the value, define the scope, and link the paper, proof, code, or reproduction that lets another person check it. Editors review every challenge before the public record changes.
Challenge this recordAssertions tied to evidence, attribution, and review.
The frontier as it changed over time.
Only accepted Claims matching the current specification contribute to the displayed bounds. Strict inequalities remain open; contradictory Claims require editorial review.
1 accepted Claim, with 1 linked evidence records.
Permanent ID limitsregistry.com/limits/LR-SUDOKU-MINIMUM-CLUES
No active verified bounties are linked to this Limit.
View verified bounty tracker ↗No accepted machine-checked reproductions are recorded for this Limit.
Limits Registry. LR-SUDOKU-MINIMUM-CLUES. Minimum number of clues in a uniquely solvable Sudoku. 2026.