Answer
$a_n=0$ and $a_{5}=0.$
Work Step by Step
We know that if $a_1$ is the first term and $r$ is the common ratio, then the nth term is: $a_n=a_1\cdot r^{n-1}.$
Hence here $a_n=0\cdot (0.5)^{n-1}=0$ and $a_{5}=0\cdot (0.5)^{5-1}=0.$
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