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Source labels openChecked July 26, 2026

Erdős ProblemsNumber theory

Erdős Problem 1212

Let GG be the graph with vertex set those pairs (x,y)N2(x,y)\in \mathbb{N}^2 with gcd(x,y)=1\mathrm{gcd}(x,y)=1, in which we join two vertices if the differ in only one coordinate, and there by ±1\pm 1.

Mathematical statement

Let GG be the graph with vertex set those pairs (x,y)N2(x,y)\in \mathbb{N}^2 with gcd(x,y)=1\mathrm{gcd}(x,y)=1, in which we join two vertices if the differ in only one coordinate, and there by ±1\pm 1.

Is there a path going to infinity on GG, say PP, such that for all (x,y)P(x,y)\in P both min(x,y)>1\min(x,y)>1 and at least one of xx or yy is composite?

The weaker version (only min(x,y)>1\min(x,y) > 1) was solved by C. Stewart via the prime-pair path (pk,pk+1)(pk+1,pk+2)(p_k, p_{k+1}) \to (p_{k+1}, p_{k+2}), as recounted in [Er80]; the compositeness condition forbids those anchors and the question is open.

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_1212

Canonical source
Complete statement target, proof intentionally absentLean 4
theorem erdos_1212 :    answer(sorry)   f :    × , Function.Injective f  ( n, Adj (f n) (f (n + 1)))       ( n, Valid (f n))       Tendsto (fun n => (f n).1 + (f n).2) atTop atTop := 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