Definition:Second Chebyshev Function

Definition

The Second Chebyshev Function $\psi \left({x}\right)$ is defined as follows:

$\displaystyle \psi \left({x}\right) = \sum_{p^k \le x} \ln p$

where the sum extends over all powers of prime numbers $p$ such that $p^k \le x$.

Equivalent definitions

The following are equivalent to the above definition:

• $\displaystyle \psi \left({x}\right) = \sum_{1 \le n \le x} \Lambda \left({n}\right)$

where $\Lambda$ is the von Mangoldt function.

• $\displaystyle \psi \left({x}\right) = \sum_{p \le x} \left \lfloor {\log_p x} \right \rfloor \ln p$

where the sum extends over all prime numbers $p$ such that $p \le x$, and $\left \lfloor {\ldots} \right \rfloor$ denotes the floor function.

Also See

Equivalence of Definitions of the Second Chebyshev Function

Source of Name

This entry was named for Pafnuty Lvovich Chebyshev.