Definition:Geometric Sequence

Definition
A geometric progression is a sequence $\left \langle{x_n}\right \rangle$ in $\R$ defined as:
 * $x_n = a r^{n-1}$ for $n = 1, 2, 3, \ldots$

where:
 * $r \in \R: r \ne 0$ is called the common ratio;
 * $a \in \R: a \ne 0$ is called the scale factor.

Thus its general form is:
 * $a, ar, ar^2, ar^3, \ldots$