Chapter 6 Elementary Results on the Distribution of Primes
Recall that the von Mangoldt function \(\Lambda\) is defined by \(\Lambda(n) = \log p\) if \(n = p^k\) is a power of a prime (\(p\) prime, \(k \geq 1\)), \(\Lambda(n) = 0\) otherwise (in particular, \(\Lambda(1) = 1\)). We consider the following three functions:
\begin{equation}
\pi(x) = \sum_{p \leq x} 1,
\qquad
\theta(x) = \sum_{p \leq x} \log p,
\qquad
\psi(x) = \sum_{n \leq x} \Lambda(n)\text{.}\tag{6.0.1}
\end{equation}
Here \(\pi\) is the prime-counting function, \(\theta\) is called Chebyshev’s \(\theta\) function, and \(\psi\) is called Chebyshev’s \(\psi\) function.