Answer :
The summation notation is ∑ [tex](4^{n} -1)\\[/tex]/2.
What is geometric progression?
The common ratio multiplied here to each term to get the next term is a non-zero number.
Given: 1/2+2+8+32+128
Using,
[tex]a_n= a_1r^{n-1}[/tex]
We have,
a1 =1/2 and r= 4
notation is : An= ∑ [tex](4^{n} -1)\\[/tex]/2
Hence, the notation is An= ∑ [tex](4^{n} -1)\\[/tex]/2.
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