3.I.1H

Number Theory | Part II, 2008

Prove that, for all x⩾2x \geqslant 2, we have

∑p⩽x1p>log⁡log⁡x−12\sum_{p \leqslant x} \frac{1}{p}>\log \log x-\frac{1}{2}

[You may assume that, for 0<u<10<u<1,

−log⁡(1−u)−u<u22(1−u).-\log (1-u)-u<\frac{u^{2}}{2(1-u)} .

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