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FormalConjectures.ErdosProblems.«288»

Erdős Problem 288 #

Reference: erdosproblems.com/288

theorem Erdos288.erdos_288 :
{I : Fin 2 × | ∃ (n : ), j : Fin 2, nⱼ(Set.Icc (I j).1 (I j).2).toFinset, (↑nⱼ)⁻¹ = n}.Finite sorry

Is it true that there are only finitely many pairs of intervals $I_1$, $I_2$ such that $$ \sum_{n_1 \in I_1} \frac{1}{n_1} + \sum_{n_2 \in I_2} \frac{1}{n_2} \in \mathbb{N}? $$

theorem Erdos288.erdos_288.variants.i2_card_eq_1 :
{(I, n₂) : ( × ) × | ∃ (n : ), n₁(Set.Icc I.1 I.2).toFinset, (↑n₁)⁻¹ + (↑n₂)⁻¹ = n}.Finite sorry

This is still open even if $|I_2| = 1$.

theorem Erdos288.erdos_288.variants.k_intervals (k : ) :
{I : Fin k × | ∃ (n : ), j : Fin k, nⱼ(Set.Icc (I j).1 (I j).2).toFinset, (↑nⱼ)⁻¹ = n}.Finite sorry

It is perhaps true with two intervals replaced by any $k$ intervals.

theorem Erdos288.erdos_288.variants.exists_k_gt_2 :
k > 2, {I : Fin k × | ∃ (n : ), j : Fin k, nⱼ(Set.Icc (I j).1 (I j).2).toFinset, (↑nⱼ)⁻¹ = n}.Finite sorry

Is it true for any $k > 2$ that only finitely many $k$ intervals satisfy this condition?