Definition:Prime-Counting Function/Examples

Definition

The values of the prime-counting ($\pi$) function for the first few integers are as follows:

$n$ $\map \pi n$
$1$ $0$
$2$ $1$
$3$ $2$
$4$ $2$
$5$ $3$
$6$ $3$
$7$ $4$
$8$ $4$

16

The value of the prime-counting ($\pi$) function for $16$ is determined as follows.

The prime numbers less than $16$ are:

$2, 3, 5, 7, 11, 13$

Hence:

$\map \pi {16} = 6$