Harmonic mean

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The harmonic mean of a finite sequence of real numbers having $n$ terms is $n$ divided by the sum of the reciprocals of the terms. For example, the harmonic mean of the first ten positive integers is approximately 3.41417152 (the reciprocals of the first 10 positive integers add up to about 2.928968 and 10 divided by that is the harmonic mean of that sequence).

The harmonic mean of any finite sequence of integers is always a rational number. The harmonic means of the first $n$ positive integers are split off into a sequence of numerators and denominators (A102928 is the former and A001008 the latter).

Compare arithmetic mean and geometric mean.