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In mathematics, a harmonic progression (or harmonic sequence) is a progression formed by taking the reciprocals of an arithmetic progression. In other words, it is a sequence of the form : where −a/''d'' is not a natural number and ''k'' is a natural number. (Terms in the form can be expressed as , we can let and .) Equivalently, a sequence is a harmonic progression when each term is the harmonic mean of the neighboring terms. It is not possible for a harmonic progression (other than the trivial case where ''a'' = 1 and ''k'' = 0) to sum to an integer. The reason is that, necessarily, at least one denominator of the progression will be divisible by a prime number that does not divide any other denominator.〔. As cited by .〕 ==Examples== :12, 6, 4, 3, , 2, … , :10, 30, −30, −10, −6, − , … , 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Harmonic progression (mathematics)」の詳細全文を読む スポンサード リンク
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