Which of these series is NOT a geometric series?
∑2⋅3n\sum 2 \cdot 3^n∑2⋅3n
∑5⋅(0.1)n\sum 5 \cdot (0.1)^n∑5⋅(0.1)n
∑n2\sum n^2∑n2
∑(1/2)n\sum (1/2)^n∑(1/2)n