Is the set of all pairs of natural numbers countable?
27937
Cartesian Product of Two Countable Sets is Countable
72750
Uncountable number of mutually disjoint countable sets in $\mathbb R$
124847
Is the set of surjective functions from $\mathbb{N}$ to $\mathbb{N}$ uncountable?
3636
Are any two uncountable sets similar to each other?
81509
The cardinality of a countable union of countable sets, without the axiom of choice
128437
How to prove that a finite set is countable
156660
The set of all strictly increasing sequences of natural numbers
11959
What's wrong with this argument that $[0,1]$ is countable?
99599
Uncountable and countable
24582
Is the set of sequences of natural numbers with trailing zeros countable?
84936
The set of all finite sequences of members of a countable set is also countable
24685
Expressing a Countable Union of Sets as the Countable Union of Disjoint Sets (e.g. Eliminating Duplicate Intersections)
68230
The cardinality of a countable union of sets with less than continuum cardinality
19297
Is the cofinite topology on an uncountable set first countable?
119084
How many ordered pairs $(A,B)$ they are if $A$ and $B$ are subsets of $\{ 1,2,3,4,5 \}$ such that $A \cap B = \{1\}$?
70196
Is there any well-ordered uncountable set of real numbers under the original ordering?
102543
Real definition of "countable set"