Suppose the coefficients ana_nan of f(x)=∑n=0∞anxnf(x) = \sum_{n=0}^{\infty} a_n x^nf(x)=∑n=0∞anxn satisfy lim supn→∞∣an∣1/n=12\limsup_{n \to \infty} |a_n|^{1/n} = \frac{1}{2}limsupn→∞∣an∣1/n=21
What is the radius of convergence?
R=12R = \frac{1}{2}R=21
R=2R = 2R=2
R=14R = \frac{1}{4}R=41
R=4R = 4R=4