If ana_nan is a geometric sequence with a1=2a_1=2a1=2 and r=1/2r=1/2r=1/2, what is ∏n=1Nan\prod_{n=1}^{N} a_n∏n=1Nan?
2N⋅2−N(N−1)/22^N \cdot 2^{-N(N-1)/2}2N⋅2−N(N−1)/2
2N−1⋅2−N(N+1)/22^{N-1} \cdot 2^{-N(N+1)/2}2N−1⋅2−N(N+1)/2
2N⋅2−N(N+1)/22^N \cdot 2^{-N(N+1)/2}2N⋅2−N(N+1)/2
2N+1⋅2−N2/22^{N+1} \cdot 2^{-N^2/2}2N+1⋅2−N2/2