Maximum number of subsets of $\{1,\ldots,n\}$ such that the intersection of every two of the subsets has cardinality $\geq r$.
73345
maximum size of a $k$-intersecting family of $[n]$
153072
Guessing a subset of $\{1,...,N\}$
40071
What is the cardinality of the set of all topologies on $\mathbb{R}$?
74311
Proving that the Intersection of any Collection of Compact Sets is Compact
85817
Show that in any set of $2n$ integers, there is a subset of $n$ integers whose sum is divisible by $n$.
82628
Cardinality of a set of closed intervals
73850
Cardinality of set of functions
7785
Cardinality of sum-set
136735
Why is the cardinality of set S is 3^n, where S is the collection of all ordered pairs of disjoint subset of {1,2,3,...,n} where n is non negative.
82207
Number of Pairs of Subsets
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...
146436
Cardinality of the set of bijective functions on $\mathbb{N}$?
83518
Proving Two sets have same cardinality
144735
Possible cardinality of power sets
5215
Can the principle of inclusion/exclusion be used to count elements in the intersection of a sequence of sets?
55648
Intersection of finite number of compact sets is compact?
158507
Max family of odd subset of a nested set.