All open problems
Source labels openChecked July 26, 2026

WikipediaNumber theory

Lonely runner conjecture

Consider nn runners on a circular track of unit length. At the initial time t=0t = 0, all runners are at the same position and start to run; the runners' speeds are constant, all distinct, and may be negative. A runner is said to be lonely at time tt if th...

Mathematical statement

Consider nn runners on a circular track of unit length. At the initial time t=0t = 0, all runners are at the same position and start to run; the runners' speeds are constant, all distinct, and may be negative. A runner is said to be lonely at time tt if they are at a distance (measured along the circle) of at least 1n\frac 1 n from every other runner. The lonely runner conjecture states that each runner is lonely at some time, no matter the choice of speeds.

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

lonely_runner_conjecture

Canonical source
Complete statement target, proof intentionally absentLean 4
theorem lonely_runner_conjecture (n : )    (speed : Fin n ↪ ) (lonely : Fin n    Prop)    (lonely_def :       r t, lonely r t          r2 : Fin n, r2  r         dist (t * speed r : UnitAddCircle) (t * speed r2)  1 / n)    (r : Fin n) :  t  0, lonely r t := 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