diff --git a/FormalConjectures/ErdosProblems/1096.lean b/FormalConjectures/ErdosProblems/1096.lean new file mode 100644 index 000000000..5b587a388 --- /dev/null +++ b/FormalConjectures/ErdosProblems/1096.lean @@ -0,0 +1,45 @@ +/- +Copyright 2025 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 1096 +*Reference:* [erdosproblems.com/1096](https://www.erdosproblems.com/1096) +-/ + +open Filter + +namespace Erdos1096 + +/-- The set of numbers of the shape ∑_{i ∈ S} q^i (for all finite S). -/ +def Sums (q : ℝ) : Set ℝ := + { s | ∃ S : Finset ℕ, s = ∑ i ∈ S, q ^ i } + +/-- +Let 1 < q < 1 + ε and consider the set of numbers of the shape ∑_{i ∈ S} q^i +(for all finite S), ordered by size as 0 = x_1 < x_2 < ... +The sequence x is strictly increasing such that its range is Sums q. +If ε > 0 is sufficiently small, then x_{k+1} - x_k → 0. +-/ +@[category research open, AMS 11] +theorem erdos_1096 : + ∃ ε > 0, ∀ q, 1 < q → q < 1 + ε → + ∀ x : ℕ → ℝ, StrictMono x → Set.range x = Sums q → + Tendsto (fun k => x (k + 1) - x k) atTop (nhds 0) ↔ answer(sorry) := + sorry + +end Erdos1096