/- Copyright 2026 The Formal Conjectures Authors. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at https://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. -/ import FormalConjecturesUtil

Erdős Problem 109

References:

    erdosproblems.com/109

    [MRR19] J. Moreira, F.K. Richter, and D. Robertson, A proof of a sumset conjecture of Erdős, Annals of Math. 189 (2019), 605-652.

open Pointwise namespace Erdos109

Any $A\subseteq \mathbb{N}$ of positive upper density contains a sumset $B+C$ where both $B$ and $C$ are infinite.

The Erdős sumset conjecture. Proved by Moreira, Richter, and Robertson [MRR19].

@[category research solved, AMS 5] theorem declaration uses 'sorry'erdos_109 (A : Set ) (h : A.upperDensity > 0) : B C : Set , B.Infinite C.Infinite B + C A := A:Set h:A.upperDensity > 0 B C, B.Infinite C.Infinite B + C A All goals completed! 🐙 end Erdos109