[seqfan] Re: intersection patterns of n sets

[Joerg Arndt]

* Neil Sloane <njasloane at gmail.com> [Dec 21. 2014 09:49]:
> 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?

Yes, of course!

> But that
> does not seem fair.

I do not understand why that should be bad:
A <==> B  is something I'd very much like to allow.


But I realize that I did not think it through:
a set not connected to any other would be forced
to be connected to that "extra set".

Anyway, I speculate this is one of the old "core" seqs.


>  If you start with three sets, then they are all
>  different
> 
> Best regards
> Neil
> 
> [...]


Best,   jj