Is there a countable basis for the finite complement topology on the natural numbers?
130361
Basis for a topology with a countable number of sets
71489
Countable product of Polish spaces
95747
Number of countable subsets of $\mathbb{R}$
7723
Countable basis of function spaces
66398
Union of a finite set and a countably infinite set is countably infinite
7678
Show "countable complement topology" is a topology
147197
Number of connected components of the complement of a compact
2403
Can a countable set contain uncountably many infinite subsets such that the intersection of any two such distinct subsets is finite?
13620
$\omega_2$ is a not countable union of countable sets without AC
133266
If $(X, \mathcal{T})$ has a countable subbasis, then it has a countable basis
40937
Is the set of partial order relations over $ \mathbb{N}$ countable?
75019
Infinite Cartesian product of countable sets is uncountable
124847
Is the set of surjective functions from $\mathbb{N}$ to $\mathbb{N}$ uncountable?
88595
Prob. 21, Sec. 17 in Munkres' TOPOLOGY, 2nd ed: Closure and complementation can result in at most 14 different sets
23442
Cardinality of the union of infinite and countable sets
68994
Countable closed sets
40071
What is the cardinality of the set of all topologies on $\mathbb{R}$?