For which of the following is the Ratio Test inconclusive?
∑1n!\sum \frac{1}{n!}∑n!1
∑2nn!\sum \frac{2^n}{n!}∑n!2n
∑1n2\sum \frac{1}{n^2}∑n21
∑n!nn\sum \frac{n!}{n^n}∑nnn!