Maybe this is the sort of question I could find the answer myself if I just knew the right search terms. I've gotten a whole bunch of search results and quite a bit of sidetracks.
In my handwritten notes, which are a little smudged and drawn from various books and journals, I have the definitions
$$f(n) = \prod_{p \mid n} p$$ is the product of primes $p$ that divide $n$
and
$$g(n) = \prod_{p \mid \mid n} p$$ is the product of primes $p$ that divide $n$ exactly
I underlined "exactly." I think those are $f$ and $g$, or they could be Greek letters, I'm not sure. This is a bit of notation I thought I copied from a Fib. Quart. article by Jean Konincke, but when I got the librarian to fetch me the article, I saw that while it does mention divisibility, it doesn't seem to distinguish between "plain" divides and "exact" divides. Also, I had the wrong author's name, though the right title.
Actually, I'm confused as to the meaning of those terms. Take $n = 28$. Wouldn't $f(n)$ be $14$ and $g(n)$ be $28$? But then what's the point of that? $f(n)$ is just the squarefree kernel of $n$, and $g(n)$ is just an identity function (presumably these are just applied to positive integers).
I'm missing something here, I must have neglected to copy the important clarifying details. Help anyone?
