Auteur: J.C. Rosales, P. A. García-Sánchez. If n .,n are positive integers with gcd{n .,n } = 1, then the set hn ., 1 e 1 e 1 n i = {?. n +··· + ?. The simplicity of this concept makes it possible to state problems that are easy to understand but whose resolution is far from being trivial.
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