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Let $A(x)=x\sum_{p \leq x} 1, B(x)=\frac{3}{5}\sum_{x Using prime number theorem, we have $A(x)\sim\frac{x^2}{\log{x}}$, but how to obtain an estimation for $B(x)$?

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    I am also puzzled about that $\frac{3}{5}$.2011-12-11

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The sum of the primes up to $x$ is, asymptotically, $(1/2)x^2/\log x$. So asymptotically, $B(x)=(3/5)((1/2)(2x)^2/\log(2x)-(1/2)x^2/\log x))$ Looks like about $(9/10)x^2/\log x$.

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    @Rob, just try to apply summation by part and use prime number theorem, you can get the asymptote directly.2011-12-11