# Definition:Harmonic Progression

## Definition

The term harmonic progression is used to mean one of the following:

### Harmonic Sequence

A harmonic sequence is a sequence $\sequence {a_k}$ in $\R$ defined as:

$h_k = \dfrac 1 {a + k d}$

where:

$k \in \set {0, 1, 2, \ldots}$
$-\dfrac a d \notin \set {0, 1, 2, \ldots}$

Thus its general form is:

$\dfrac 1 a, \dfrac 1 {a + d}, \dfrac 1 {a + 2 d}, \dfrac 1 {a + 3 d}, \ldots$

### Harmonic Series

The series defined as:

$\ds \sum_{n \mathop = 1}^\infty \frac 1 n = 1 + \frac 1 2 + \frac 1 3 + \frac 1 4 + \cdots$

is known as the harmonic series.