# Definition:Deficient Number/Definition 1

## Definition

Let $n \in \Z_{\ge 0}$ be a positive integer.

Let $A \left({n}\right)$ denote the abundance of $n$.

$n$ is deficient if and only if $A \left({n}\right) < 0$.

## Sequence

The sequence of deficient numbers begins:

$2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 21, \ldots$