diff --git a/FormalConjectures/ErdosProblems/1210.lean b/FormalConjectures/ErdosProblems/1210.lean new file mode 100644 index 0000000000..4dfaa6cc37 --- /dev/null +++ b/FormalConjectures/ErdosProblems/1210.lean @@ -0,0 +1,60 @@ +/- +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 FormalConjectures.Util.ProblemImports + +/-! +# Erdős Problem 1210 + +*References:* +- [erdosproblems.com/1210](https://www.erdosproblems.com/1210) +- [Er77c] Erdős, Paul, Problems and results on combinatorial number theory. III. Number theory day + (Proc. Conf., Rockefeller Univ., New York, 1976) (1977), 43-72. +- [Er80] Erdős, Paul, A survey of problems in combinatorial number theory. Ann. Discrete Math. + (1980), 89-115. +-/ + +open Finset + +namespace Erdos1210 + +/-- +Let $A\subseteq [1,n)$ be a set of integers such that $(a,b)=1$ for all distinct $a,b\in A$. +Is it true that $\sum_{a\in A}\frac{1}{n-a}\leq \sum_{p < n}\frac{1}{p}+O(1)$? +-/ +@[category research open, AMS 11] +theorem erdos_1210 : + answer(sorry) ↔ + ∃ C : ℝ, ∀ n : ℕ, ∀ A : Finset ℕ, + (∀ a ∈ A, 1 ≤ a ∧ a < n) → + (∀ a ∈ A, ∀ b ∈ A, a ≠ b → a.Coprime b) → + ∑ a ∈ A, (1 / ((n : ℝ) - a)) ≤ (∑ p ∈ (range n).filter Prime, (1 / (p : ℝ))) + C := by + sorry + +/-- +In [Er80] he claims he "did not state this quite correctly" in [Er77c]. The problem in [Er77c] which +Erdős is presumably referring to states that if $n < q_1 < \cdots < q_k\leq m$ is the set of primes +in $(n,m]$ then $\sum \frac{1}{q_i-n} < \sum_{p < m-n}\frac{1}{p}+O(1)$. +-/ +@[category research open, AMS 11] +theorem erdos_1210.variants.er80_correction : + answer(sorry) ↔ + ∃ C : ℝ, ∀ n m : ℕ, n < m → + ∑ q ∈ (Ioc n m).filter Prime, (1 / ((q : ℝ) - n)) < + (∑ p ∈ (range (m - n)).filter Prime, (1 / (p : ℝ))) + C := by + sorry + +end Erdos1210