All open problems
Source labels openChecked July 26, 2026
Packing
What is the smallest square that can contain 21 unit circles?
Mathematical statement
What is the smallest square that can contain 21 unit circles?
Statement source: Wikipedia statement material
Statement terms: CC-BY-SA-4.0
Attributed source material. Reuse must follow the linked attribution and share-alike terms.
Statement artifacts, not proofs
These records expose exact Lean propositions and statement-only wrappers. Defining a proposition does not supply a proof of it. A placeholder-bearing target also contains no proof. Elaboration checks syntax and types; it does not certify that a formalization perfectly captures every nuance of the informal problem.
Pinned Lean formulation 1
least_twenty_one_circle_packing_in_square
Complete statement target, proof intentionally absentLean 4
theorem least_twenty_one_circle_packing_in_square : IsLeast {x : ℝ | Nonempty (Packing 21 UnitCircle (Square x))} answer(sorry) := by sorry- Statement source
- Formal Conjectures
- Lean version
- v4.27.0
- Placeholder
- Present; no proof artifact
- Source evidence
- Pinned source index
- Fidelity review
- Community formulation
References