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Re: cotpi 41 - Counting locally prime numbers
Posted:
Feb 27, 2012 2:07 PM
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"Tonico" <Tonicopm@yahoo.com> wrote in message
news:f3c955d7-13fd-4f4a-bdcd-411c06f2c280@do4g2000vbb.googlegroups.com...
> On Feb 27, 8:50 am, cotpi <puzz...@cotpi.com> wrote:
...
> >
> > Let A be a set of 10 consecutive integers. Let B be a subset of A such
> > that every element in A that is coprime to every other element in A is
> > present in B. What are the possible values for the cardinality of B?
> >
> > I hope this helps.
> >
> > cotpi
>
>
>
> Take the set A:= {10, 11,..., 19} . As with any other of the given
> characteristics, it has exactly 5 even numbers and 5 odd numbers, and
> according to the presented condition NONE of the even numbers can be
> present in the wanted subset B (as any of these ones is NOT coprime
> with any other even element in A).
No, you're misreading (or I am...)
For A:= {10, 11,..., 19} we can have B:= A. (In fact, we can do this for
any A.)
Mike.
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