Why $O(n)$ has exactly two connected components?
114987
How many connected components does $\mathrm{GL}_n(\mathbb R)$ have?
145718
Proving that A connected graph on $n$ vertices is a tree iff it has $n-1$ edges
71154
Why a complete graph has $\frac{n(n-1)}{2}$ edges?
74730
Combinatorial Proof of ${{n}\choose{k}} {{k}\choose{j}} = {{n}\choose{j}} {{n-j}\choose{k-j}}$
123742
Proving connectedness of the $n$-sphere
83615
split conjugacy class in $S_n$ into two equal size conjugacy classes in $A_n$
70761
Number of ways to connect sets of $k$ dots in a perfect $n$-gon
84492
Can $X$ have compact connected components?
102084
How to show path-connectedness of $GL(n,\mathbb{C})$
114752
Number of permutations of a specific cycle decomposition
114990
Is the complement of countably many disjoint closed disks path connected?
140199
Proof that disjoint cycles commute
23225
Union of connected subsets is connected if intersection is nonempty
154754
Is $O_n$ isomorphic to $SO_n \times \{\pm I\}$?
86342
Why does $\log(n!)$ and $\log(n^n)$ have the same big-O complexity?
104010
The number of partitions of $n$ into distinct parts equals the number of partitions of $n$ into odd parts
57954
How many transitive relations on a set of $n$ elements?