The Erdős-Szekeres Theorem
71159
Example of Erdos-Szekeres bound being tight
55199
Number Theory in a Choice-less World
41726
Musical and combinatorial proof
96803
Hall's marriage theorem in bipartite graph
157079
Maximal cardinality of a family of pairwise disjoint "figure eights" in the plane
46550
Proving an 'obvious' Ramsey upperbound
1495
The Frobenius Coin Problem
94058
Applying the Berry-Esseen theorem to non-identically distributed summands
130771
Sets and the principle of inclusion and exclusion
79974
The cardinality of Lebesgue sets
111032
Proof of Sets involving the Cartesian Product
4776
Prove that the power set of an $n$-element set contains $2^n$ elements
101179
Partition of a set and Hall's theorem
117862
Number of partitions of an $n$-element set into $k$ classes
74311
Proving that the Intersection of any Collection of Compact Sets is Compact
68230
The cardinality of a countable union of sets with less than continuum cardinality
12436
The cardinality of the set of all finite subsets of an infinite set