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Erdős problem 287

Let k≥2k\geq2. Is it true that, for any distinct integers 1<n1<⋯<nk1 < n_1 < \cdots < n_k such that ∑i=1k1ni=1\sum_{i=1}^k \frac{1}{n_i} = 1, we must have max⁡(ni+1−ni)≥3\max(n_{i+1} - n_i) \geq 3?

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FormalConjectures/ErdosProblems/

287.lean

Retained formal statement5 of 5

The conjecture erdos_287 would follow for all but at most finitely many exceptions if it were known that, for all large NN, there exists a prime p∈[N,2N]p \in [N, 2N] such that p+12\frac{p+1}{2} is also prime.

More precisely: if the prime conjecture holds, then there exists k0k_0 such that for all k≥k0k \geq k_0, any Egyptian fraction representation of 11 with kk terms and all terms >1> 1 must have max⁡(ni+1−ni)≥3\max(n_{i+1} - n_i) \geq 3.

FormalConjectures/ErdosProblems/287.leanErdos287.erdos_287.variants.prime_conjecture_implies5 linesExact file
(True ↔ ∃ N₀, ∀ (N : ℕ), N₀ ≤ N → ∃ p, Nat.Prime p ∧ N ≤ p ∧ p ≤ 2 * N ∧ Nat.Prime ((p + 1) / 2)) →  ∃ k₀,    ∀ (k : ℕ),      k₀ ≤ k →        ∀ (hk : 2 ≤ k) (s : Fin k → ℕ), StrictMono s → 1 < s ⟨0, ⋯⟩ → ∑ i, 1 / ↑(s i) = 1 → 3 ≤ Erdos287.max_gap k s
TextbookStatement only, no proof