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FormalConjectures.ErdosProblems.«488»

Erdős Problem 488 #

Reference: erdosproblems.com/488

theorem Erdos488.erdos_488 :
(∀ (A : Finset ), A.Nonempty0A1A∀ (n m : ), m > nA.max n{xFinset.Icc 1 m | x {n : | n 1 aA, ¬a n}}.card / m < 2 * {xFinset.Icc 1 n | x {n : | n 1 aA, ¬a n}}.card / n) False

Let $A$ be a finite set and $$B = \{n \ge 1 : a \nmid n \text{ for all } a \in A\}.$$ Is it true that, for every $m > n \ge \max(A)$, $$\frac{|B \cap [1, m]|}{m} < 2 \frac{|B \cap [1, n]|}{n}?$$