ISL 2007 N6
Let be a positive integer. Prove that the number has a positive divisor of the form if and only if is even. (United Kingdom)
Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.
Official text: IMO 2007 Shortlist booklet, page 63.
Solutions
Official solution Solution 1 by the IMO Problem Selection Committee
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