For ∑n=1∞n2n\sum_{n=1}^{\infty} \frac{n}{2^n}∑n=1∞2nn, compute limn→∞an+1an\lim_{n \to \infty} \frac{a_{n+1}}{a_n}limn→∞anan+1.
000
12\frac{1}{2}21
111
222