Source labels openChecked July 26, 2026

Erdős Problem 107

Let $f(n)$ be minimal such that any $f(n)$ points in $ℝ^2$ , no three on a line, contain $n$ points which form the vertices of a convex $n$ -gon. Prove that $f(n) = 2^{n-2} + 1$ .

Convex geometry AMS 52

Mathematical statement

Let $f(n)$ be minimal such that any $f(n)$ points in $ℝ^2$ , no three on a line, contain $n$ points which form the vertices of a convex $n$ -gon. Prove that $f(n) = 2^{n-2} + 1$ .

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_107

Canonical source

Complete statement target, proof intentionally absentLean 4

theorem erdos_107 : answer(sorry) ↔ ∀ n ≥ 3, f n = 2^(n - 2) + 1 := 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

Pinned Formal Conjectures sourceformalization erdosproblems.com/107background Wikipediabackground