[tex]\bf \textit{a geometric sequence}
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2,~~\stackrel{2\cdot 2}{4},~~\stackrel{2\cdot 4}{8},~~\stackrel{2\cdot 8}{16},...
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\cfrac{4}{2}\implies \stackrel{ratio}{2}\qquad \qquad \cfrac{8}{4}\implies \stackrel{ratio}{2}\qquad \qquad \cfrac{16}{8}\implies \stackrel{ratio}{2}
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