# harmonic number

## English

### Noun

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harmonic number (plural harmonic numbers)

1. (number theory) Any of a series of numbers formed from the sum of the reciprocals of consecutive natural numbers
The fourth harmonic number has a value of $H_3 =\sum_{k=1}^3 \frac{1}{k} =\frac{1}{1}+\frac{1}{2}+\frac{1}{3} =1\frac{5}{6} .$