Dedekind psi-function
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This article defines an arithmetic function or number-theoretic function: a function from the natural numbers to a ring (usually, the ring of integers, rational numbers, real numbers, or complex numbers).
View a complete list of arithmetic functions
Definition
The Dedekind psi-function is an arithmetic function that sends any natural number 
to the number:
where the product is over all primes 
dividing .
Relation with other arithmetic functions
- Euler phi-function has a similar expression to the Dedekind psi-function, except that the expression is
rather than 
.
