Answer
An explicit rule for the sequence is
$ a_n=16(0.5)^{n-1}$
Work Step by Step
The given recursive rule is
$a_1=16,a_n=0.5a_{n-1}$
First term is $a_1=16$.
and common ratio $r=0.5$.
Explicit rule for an geometric sequence.
$\Rightarrow a_n=a_1r^{n-1}$
Substitute $16$ for $a_1$ and $0.5$ for $d$.
$\Rightarrow a_n=16(0.5)^{n-1}$
