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Ramiro de la Vega
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Your two examples are of the following form: Fix a collection $C$ of subsets of $n$ such that any two elements of $C$ have non-empty intersection and any other subset of $n$ either contains or is disjoint from an element of $C$. Then let $A$ be the collection of those subsets of $n$ which contain an element of $C$.

In the first example $C=\{\{0\}\}$ while in the second example $C$ is the collection of subsets of size $(n+1)/2$. It is not hard to show that any example must be of this form.

Actually, a family $A$ satisfy conditions $1$ and $2$ if and only if $A$ is a maximal intersecting family. Here intersecting means that the intersection of any two members of the family is non-empty.

Ramiro de la Vega
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