\begin{definition}[Definition:Harmonic Sequence/Common Difference]
Let $\sequence {h_k}$ be the harmonic sequence:
:$a_k = \dfrac 1 {a + k d}$ for $k = 0, 1, 2, \ldots$
The term $d$ is the '''common difference''' of $\sequence {a_k}$.
Category:Definitions/Harmonic Sequences
\end{definition}