Talk:Schnirelmann density

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In the section on Waring's problem we find this statement:

r_N^k(n) \leftrightarrow n \in N\mathfrak{G}^k,

I think this should be r_N^k(n) > 0 \leftrightarrow n \in N\mathfrak{G}^k,, assuming that N\mathfrak{G}^k means the N-fold set sum of \mathfrak{G}^k. As it stands I cannot make sense of the statement, as r_N^k(n) is a number, not a statement. Molinari 00:56, 19 October 2005 (UTC)

I agree - it only makes sense for a statement and not a number, so I have changed it. Madmath789 07:39, 28 June 2006 (UTC)

[edit] more help needed

Hello! The sharp symbol "#" is used here but not listed in in the Mathematical notation article.

Where should one find an explanation for that symbol (I ignore its meaning), and where this question must be posted for a quick answer ?

Thnks, --DLL 20:00, 27 June 2006 (UTC)

The symbol "#" is used in front of a set to indicate the number of elements in the set, so #{2,4,6,8} = 4. In the article, \#(A \cap \{1, 2, \ldots n\}) is the number of elements of A which are in the set {1, 2, 3, ..., n}. Hope that helps! Madmath789 21:00, 27 June 2006 (UTC)
Thank you! The table used in Table of mathematical symbols is quite complex and I do not want to break it. I'll add a comment for some help there with your indications. --DLL 17:38, 28 June 2006 (UTC)
That's the first time I've ever seen #. Why not go with the standard |A \cap \{1, 2, \ldots n\}| set cardinality operator here? TomJF 06:02, 5 September 2006 (UTC)
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