Let {an : n ≥ 1} n be a sequence of real numbers such that \( \sum_{n=1}^{\infty} a_{n}\) is convergent and \(\sum_{n=1}^{\infty}\left|a_{n}\right|\) is divergent. Let R be the radius of convergence of the power series \(\sum_{n=1}^{\infty} a_{n} x^{n}\). Then we can conclude that
1
0 < R < 1
2
R = 1
3
1 < R < ∞
4
R = ∞