Erdős problem 45Let k≥2k\geq 2. Is there an integer nkn_k such that, if D={1<d<nk:d∣nk}D=\{ 1<d<n_k : d\mid n_k\}, then for any kk-colouring of DD there is a monochromatic subset D′⊆DD'\subseteq D such that ∑d∈D′1d=1\sum_{d\in D'}\frac{1}{d}=1?WorkspaceContinue locallyOpen sourceSign in to contributeOpen this exact Problem, source revision, and authority Repository in Workbench. This handoff does not clone, switch, upload, or execute anything.FilesErdős problem 454 retained source recordsCanvaspublic previewSource#45→ResultNone→Checks0