Question 149448
{{{a[1]=5}}}


Since {{{a[n]=2a[n-1]}}}, this means that...


when n=2, then 


{{{a[2]=2a[2-1]=2a[1]=2(5)=10}}}



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when n=3, then 


{{{a[3]=2a[3-1]=2a[2]=2(10)=20}}}



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So the sequence is 5,10,20. So you are correct.