Which answer represents the series in sigma notation?


1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64


7

A. ∑ 2^j-1

j=1


7

B. ∑ 1/2(j+1)

j=1


7

C. ∑ 1/2 ^j-1

j=1


7

D. ∑ 1/2j+1

j=1