Construct an Injection between the set of rationals $\mathbb{Q}$ and the set of all integers $ \mathbb{Z}$
34998
How to prove that $\mathbb{Q}$ ( the rationals) is a countable set
146617
A complete picture of the lattice of subfields for a cyclotomic extension over $\mathbb{Q}$.
42213
Computing $\text{Gal}(\mathbb{Q}^{ab}/\mathbb{Q})$
86877
Let $F$ be a Galois extension over $\mathbb{Q}$ with $[F:\mathbb{Q}]=2^n$, then all elements in $F$ are constructible
152638
The set of integers $n$ expressible as $n=x^2+xy+y^2$
59134
Proving idempotent elements in $\mathbb{Z}_n$
72144
Show that $\mathbb Q(\sqrt p) \not\simeq\mathbb Q(\sqrt q)$
157915
Isomorphism between the group $(\mathbb Z[x], +)$ and $(\mathbb Q_{>0}, .)$
117132
Rationals of the form $\frac{p}{q}$ where $p,q$ are primes in $[a,b]$
51695
Finding all homomorphisms between $\mathbb{Z}/m\mathbb{Z}$ and $\mathbb{Z}/n\mathbb{Z}$
40162
Prove that the set $\mathbb{Q}[\alpha] = \{a+b\alpha+c\alpha^2 \mid a, b, c \in\mathbb{Q}\}$ is closed under addition and multiplication.
28692
Find if set $I$ of all injective functions $\mathbb{N} \rightarrow \mathbb{N}$ is equinumerous to $\mathbb{R}$
114442
Completion of rational numbers via Cauchy sequences
135611
Extensions of $\mathbb{Z}$ by $\mathbb{Z}$
145039
Algebraic independence over $\overline{\mathbb Q}$ and over $\mathbb Q$
59535
Prove that there exists such a set of $n$ positive integers
143831
Showing $\mathbb{Q}$ is homeomorphic to $\mathbb{Q}^2$