The set $\{\frac{\varphi(n)}n:n\in \Bbb N\}$
158582
Prove that $\{\frac{\phi (n)}{n}\}_{n \in \Bbb N}$ is dense in $[0,1]$
53593
Limits of sequences of sets
141531
Find the set of $n\in\Bbb Z^+$ with $M=\{n,n+1,n+2,n+3,n+4,n+5\}$ partitionable into two sets
30105
Multiples of an irrational number forming a dense subset
137711
Alternative proof that $[\Bbb{Q}(\zeta_n) : \Bbb{Q} ]= \varphi(n)$ uses circular reasoning?
70164
Proof exercise that the cardinal number of a set in $\mathbb R^2$ is $\frak c$
59885
Proof Verification - Every sequence in $\Bbb R$ contains a monotone sub-sequence
96845
Question: Compare the cardinality between the sets $\Bbb R$ and $\Bbb N^{\Bbb N}$
110662
Show that $P(\mathbb{N})$ is equivalent to $2^\mathbb{N}$
6161
The cartesian product $\mathbb{N} \times \mathbb{N}$ is countable
96931
Supremum and infimum of $\{\frac{1}{n}-\frac{1}{m}:m, n \in \mathbb{N}\}$
30630
Proving ${n \choose p} \equiv \Bigl[\frac{n}{p}\Bigr] \ (\text{mod} \ p)$
84871
Determining the dimension of span$\{AB-BA : A,B \in M_{n \times n}(\mathbb R) \}$
50880
Expressing $\Bbb N$ as an infinite union of disjoint infinite subsets.
41052
The set of real numbers and power set of the natural numbers
151686
A proof that the Cantor set is Perfect
80350
$\limsup \frac{a_n}{b_n}0$ s.t $a_n\le Mb_n$