About certain proof of countability of $\mathbb{Q}$
5803
Produce an explicit bijection between rationals and naturals?
67066
Proof there is a 1-1 correspondence between an uncountable set and itself minus a countable part of it
138768
Showing that the family of Borel sets is countably generated
129109
Is the set of polynomial with coefficients on $\mathbb{Q}$ enumerable?
68139
Show that the set of polynomials with rational coefficients is countable.
41661
Show that the set of all finite subsets of $\mathbb{N}$ is countable.
95240
Show that $({\mathbb{Q}},+)$ is not finitely generated using the Fundamental Theorem of Finitely Generated Abelian Groups.
3296
Proof That $\mathbb{R} \setminus \mathbb{Q}$ Is Not an $F_{\sigma}$ Set
11710
How to show that $\mathbb{Q}$ is not $G_\delta$
119549
Prove the even integers are countable (by explicitly giving a bijection $\mathbb{N} \to E$)
18223
Prove that the union of two disjoint countable sets is countable
84936
The set of all finite sequences of members of a countable set is also countable
35692
The set of all finite subsets of the natural numbers is countable
61103
Prove that $\mathbb{|Q| = |Q\times Q|}$
143831
Showing $\mathbb{Q}$ is homeomorphic to $\mathbb{Q}^2$
134844
Summablity and countability
41035
Mapping that proves $\mathbb{Z} \subset \mathbb{Q}$