Definition:Thabit Number

Definition
A Thabit number is an integer in the form:
 * $3 \times 2^n - 1$

where $n \in \Z_{\ge 0}$ is a non-negative integer.

Also known as
A Thabit number is also known as a 321 number, from its form: $3$ times $2$ to the $n$th minus $1$.

Some sources give his name in full, or a rendition of it: Thâbit ibn Kurrah number.

The shorter form is preferred on.