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Source labels openChecked July 26, 2026

Erdős ProblemsNumber theory

Erdős Problem 331: Ruzsa

Ruzsa suggests that a non-trivial variant of this problem arises if one imposes the stronger condition that A{1,,N}cAN1/2|A \cap \{1,\dots,N\}| \sim c_A N^{1/2} for some constant cA>0c_A>0, and similarly for BB.

Mathematical statement

Ruzsa suggests that a non-trivial variant of this problem arises if one imposes the stronger condition that A{1,,N}cAN1/2|A \cap \{1,\dots,N\}| \sim c_A N^{1/2} for some constant cA>0c_A>0, and similarly for BB.

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_331.variants.ruzsa

Canonical source
Complete statement target, proof intentionally absentLean 4
theorem erdos_331.variants.ruzsa :    answer(sorry)        A B : Set ,      ( c_A > 0, (fun (n : )  (count A n : )) ~[atTop] (fun (n : )  c_A * (n : ) ^ (1 / 2 : )))       ( c_B > 0, (fun (n : )  (count B n : )) ~[atTop] (fun (n : )  c_B * (n : ) ^ (1 / 2 : )))       { s :  ×  ×  ×  | let a₁, a₂, b₁, b₂ := s        a₁  A  a₂  A  b₁  B  b₂  B         a₁  a₂  a₁ + b₂ = a₂ + b₁ }.Infinite := 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