[seqfan] Re: intersection patterns of n sets

[Neil Sloane]

With 2 sets, they are disjoint, or one contains the other, or they have
a nontrivial intersection, which is three ways, and 3 is not
a term of A000088.

So I don't understand your remark.

Perhaps you were thinking the sets could also be equal? But that
does not seem fair.  If you start with three sets, then they are all
 different

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com


On Sat, Dec 20, 2014 at 4:49 AM, Joerg Arndt <arndt at jjj.de> wrote:
>
> Removing all "geometric" restrictions from
>   https://oeis.org/A250001
> and changing "circles" to "sets" we get a
> comment that could possibly put into some(*)
> sequence:
>
> "a(n+1) is the number of intersection patterns
> of n (unlabeled) sets of unlabeled elements."
>
>
> Now which one would be (*)?
> Spoiler below.
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> SPOILER:
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> Comment goes on:
> "Take n nodes for the sets and put an edge between to
> sets whenever they have a nonempty intersection;
> take one extra node and put an edge to a set whenever
> it has an element that is unique to it."
>
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> Yes, sequence (*) is
>   https://oeis.org/A000088
>
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> Is this a comment worthy of being put into A000088 ?
>
> If so, should a similar comment appear in
>   https://oeis.org/A001349
> ?
>
> Best regards,  jj
>
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