Paper 4, Section I, G

Number Theory | Part II, 2017

Show that, for x⩾2x \geqslant 2 a real number,

∏p⩽xp is prime (1−1p)−1>log⁡x\prod_{\substack{p \leqslant x \\ p \text { is prime }}}\left(1-\frac{1}{p}\right)^{-1}>\log x

Hence prove that

∑p⩽x,p is prime 1p>log⁡log⁡x+c,\sum_{\substack{p \leqslant x, p \text { is prime }}} \frac{1}{p}>\log \log x+c,

where cc is a constant you should make explicit.

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