$\sum_{n=0}^{\infty} \frac{x^n}{2^{n+1}}$, $R=2$

$\sum_{n=0}^{\infty} \frac{x^n}{2^n}$, $R=1$

$\sum_{n=0}^{\infty} \frac{x^{n+1}}{2^n}$, $R=2$

$\sum_{n=0}^{\infty} \frac{x^n}{2^{n+1}}$, $R=1$