Sunday, 30 November 2014

elementary number theory - Notation for "the highest power of $p$ that divides $n$"




If $p$ is a prime and $n$ an integer, is there a standard or commonly used notation for "the highest power of $p$ that divides $n$"?



It's a concept that is often used repeatedly in number-theoretic proofs (see for example this answer), and a convenient notation could make such proofs much more concise. This answer uses the notation $\{n,p\}$, which is convenient but seems not to be widely used.



Edit: Prompted by Thomas Kildetoft's comment below, by a convenient notation I mean one which facilitates not only simple statements such as:




  • $m$ is the highest power of $p$ that divides $n$.




but also more complex statements such as:




  • $m$ = (The highest power of $p$ that divides $n$) + 1


Answer



Yes, there is a standard notation, namely $p^e\mid\mid n$, which says that $e$ is the largest power of $p$ which divides $n$.



Reference: Martin Aigner, Number Theory.




Edit: For more advanced purposes, like $p$-adic numbers etc., a common notation is also $\nu_p(n)$, which also then appears in more elementary context. For elementary number theory I have seen $p^e\mid\mid n$ more often, though.


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