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\begin{document}
$$
x[n]=\{...,0.5^{{-3}},0.5^{{-2}},0.5^{{-1}},1,0.5,0.5^{2},0.5^{3},...\}=\{...,2^{3},2^{2},2,1,0.5,0.5^{2},0.5^{3},...\}\ 
$$
\end{document}
