For which $t \in \mathbb{N}$ does $\varphi(t) \mid t$?
46065
How do you find all $n$ such that $\phi(n)|n$
109498
Linear maps $f: M_n \longrightarrow \mathbb{R}$ such that $f(AB) = f(BA)$
12293
Let X be a T1 space, and show that X is normal if and only if each neighbourhood of a closed set F contains the closure of some neighbourhood of F
117793
Finding a function $\mathbb{N} \to \mathbb{N}$ that is surjective but not injective.
77957
How is $\mathbb N$ actually defined?
59724
Proving that $x_n\to L$ implies $|x_n|\to |L|$, and what about the converse?
12100
$n \mid (a^{n}-b^{n}) \ \Longrightarrow$ $n \mid \frac{a^{n}-b^{n}}{a-b}$
63104
Dual cone of $K = \{(x,t) \mid \| \boldsymbol{x} \|_1 \le t \}$
124333
A bijection between $\mathbb{N}$ and $\mathbb{P}(\mathbb{N})$?
59424
Showing that $B=\{(x,y) \in \Bbb{R^2} \mid \ xy>0 \}$ is an open set
36747
$\text{Tor}_0^R(M,N)\simeq M\otimes_R N$
148901
Can a composite number $n$ be the arithmetic mean of $\sigma(n)$ and $\varphi(n)$?
92975
Does $a^n \mid b^n$ imply $a\mid b$?
125966
Why there's a finite $\Gamma '$ such that $\Gamma ' \vDash \varphi$?
127488
If $L:\mathbb{R}^n \rightarrow \mathbb{R}^m$ and $m<n$ linear trans. What does this tell about injectivity and surjectivity?
10236
Show that $a^n \mid b^n$ implies $a \mid b$
51687
Is the set $ \ (\mathbb{Z}_p \setminus \mathbb{Z}) \cap \mathbb{Q}$ non-empty?