Answer
$\left\{
1,3,9,27,81
\right\}
$
Work Step by Step
Given that $
a_n=3^{n-1}
$, then the first 5 terms are
\begin{array}{l}
a_1=3^{1-1}\\
a_1=3^{0}\\
a_1=1
,\\\\
a_2=3^{2-1}\\
a_2=3^{1}\\
a_2=3
,\\\\
a_3=3^{3-1}\\
a_3=3^{2}\\
a_3=9
,\\\\
a_4=3^{4-1}\\
a_4=3^{3}\\
a_4=27
,\\\\
a_5=3^{5-1}\\
a_5=3^{4}\\
a_5=81
.\end{array}
Hence, the first 5 terms are $
\left\{
1,3,9,27,81
\right\}
$.