A Sequence $a_{n}$ Can Be Defined by a Recurrence Relation, Which Gives the Which

Short Answer

A sequence $a_{n}$ can be defined by a recurrence relation, which gives the first term, $a_{1}$ , and a formula for finding $a_{n}$ in terms of the previous term, $a_{n-1}$ . For the recurrence relation below, what is $a_{4}$ ?
$a_{1}=5 ; a_{n}=\frac{a_{n-1}}{2}$