Which of these is NOT a series?
∑n=1∞1n\sum_{n=1}^{\infty} \frac{1}{n}∑n=1∞n1
11+12+13+…\frac{1}{1} + \frac{1}{2} + \frac{1}{3} + \dots11+21+31+…
1n\frac{1}{n}n1
∑n=110n2\sum_{n=1}^{10} n^2∑n=110n2