Mertens theorem for reciprocal primes (source code)

= Mertens theorem for reciprocal primes
{c}

There is an absolute constant $B_1$, the Meissel–Mertens constant, such that
$$
\sum_{p\leq x}\frac1p
=\log\log x+B_1+O\left(\frac1{\log x}\right).
$$