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How to count elements

by epsi00
Tags: elements
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Feb24-12, 10:02 AM
P: 894
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We can perhaps interpret the question as follows:

Let u(n) be the cardinality of the set {a*b: a,b in {1,2,...,n}}. For example, u(3)=6 and u(7)=25. Is there some kind of general formula, or a clever way to determine u(n)?

In particular, what is u(1000)?
That is right but no formula apparently exists for u(n) but see

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