Graduate School of Mathematics, Kyushu University 33, Fukuoka 812-8581, Japan ; Faculty of Mathematics, Kyushu University 33, Fukuoka 812-8581, Japan
Abstract:
A positive integer is said to be harmonic when the harmonic mean of its positive divisors is an integer. Ore proved that every perfect number is harmonic. No nontrivial odd harmonic numbers are known. In this article, the list of all harmonic numbers with is given. In particular, such harmonic numbers are all even except .