how to count elements

epsi00

Thank you Office Shredder. What I meant was in fact that simple.

Let's even write it as M(i,j)=i*j for i=j=1,n.

ramsey2879

Quote by Norwegian

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 https://oeis.org/A027424

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epsi00	how to count elements Thank you Office Shredder. What I meant was in fact that simple. Let's even write it as M(i,j)=i*j for i=j=1,n.