All open problems
Source labels openChecked July 26, 2026
Erdős Problem 7
Is there a covering system all of whose moduli are odd (and greater than 1)?
Mathematical statement
Is there a covering system all of whose moduli are odd (and greater than 1)?
Statement source: Erdős Problems statement material
Statement terms: Source-specific
Source-specific terms. Therefore does not assert reuse rights beyond attributed display.
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
erdos_7
Complete statement target, proof intentionally absentLean 4
theorem erdos_7 : answer(sorry) ↔ ∃ (C : StrictCoveringSystem ℤ), ∀ i, ¬ C.moduli i ≤ Ideal.span {2} ∧ C.moduli i ≠ ⊤ := 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