Which series is NOT an alternating series?
∑n=1∞1n2\sum_{n=1}^{\infty} \frac{1}{n^2}∑n=1∞n21
∑n=1∞(−1)nn\sum_{n=1}^{\infty} \frac{(-1)^n}{n}∑n=1∞n(−1)n
∑n=1∞cos(nπ)1n\sum_{n=1}^{\infty} \cos(n\pi)\frac{1}{n}∑n=1∞cos(nπ)n1
∑n=1∞(−1)n+1nn+1\sum_{n=1}^{\infty} (-1)^{n+1}\frac{n}{n+1}∑n=1∞(−1)n+1n+1n