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From: jkpachl@watdaisy.UUCP (Jan Pachl)
Newsgroups: sci.math
Subject: A combinatorial problem: Do some n sets intersect?
Message-ID: <7978@watdaisy.UUCP>
Date: Sun, 9-Nov-86 13:22:05 EST
Article-I.D.: watdaisy.7978
Posted: Sun Nov  9 13:22:05 1986
Date-Received: Sun, 9-Nov-86 21:03:05 EST
Distribution: sci
Organization: U of Waterloo, Ontario
Lines: 15

::
I would appreciate any reference for the following
(unsolved, as far as I know) combinatorial problem:

Let  n > 0  be an integer, and let  A  be a collection
of  2n  sets.  Let  A  be closed under union (i.e. if two
sets belong to  A  then their union belongs to  A  as well).
Is it always true (i.e. for any  n  and any such  A ) that
some  n  sets in  A  intersect?

Apparently Erdos proposed the problem during one of his problem
talks, several years ago.  Is the problem recorded anywhere?
(If there is a solution, I'll take that, too).

Jan Pachl,   University of Waterloo