MathDB
O 40

Source:

May 25, 2007
floor functioninductionlogarithms

Problem Statement

Let XX be a non-empty set of positive integers which satisfies the following: [*] if x∈Xx \in X, then 4x∈X4x \in X, [*] if x∈Xx \in X, then ⌊x⌋∈X\lfloor \sqrt{x}\rfloor \in X. Prove that X=NX=\mathbb{N}.
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