Sets of size 45 with pairwise intersections having 1 element
130771
Sets and the principle of inclusion and exclusion
136108
Arbitrary intersection of closed, connected subsets of a compact space connected?
135743
Collection of subset generating every pairs of elements
11849
Size of a union of two sets
130156
Image of the union and intersection of sets.
158882
Prove the existence of some weird family of sets
26569
Counting binary operations on a set with $n$ elements
73345
maximum size of a $k$-intersecting family of $[n]$
36789
The power set of the intersection of two sets equals the intersection of the power sets of each set
86902
Consider the smallest number in each of the $n\choose r$ subsets (of size $r$) of $S=\{1,2,\ldots,n\}$...
5118
Show that $n ≤ 100$ if $ \{A_1,A_2,... ,A_n\}$ is a set of distinct $3$-element subsets of $\{1, 2,... , 36\}$ such that...
23225
Union of connected subsets is connected if intersection is nonempty
111954
Computing the cardinality of a combinatorial set
69748
Semi-Ambiguous Combinatorics Problem
132068
Write the set $\{1, 6, 11, 16,\ldots\}$ in compact (concise) notation.
17703
$S$ be a collection of subsets of $\{1,...,100\}$ ; any two sets in $S$ has non-empty intersection , what is the maximum possible value of $|S|$?
128844
An empty intersection of decreasing sequence of closed sets