How many reflexive relation are there on a set with n elements?
1643
Number of reflexive relations defined on a set A with n elements
117862
Number of partitions of an $n$-element set into $k$ classes
88595
Prob. 21, Sec. 17 in Munkres' TOPOLOGY, 2nd ed: Closure and complementation can result in at most 14 different sets
62687
Proving Cardinality of Cosets in Abstract Algebra
95747
Number of countable subsets of $\mathbb{R}$
42603
How can I prove that the cadinality of a set minus a finite number of elements of it is still the same as the original set?
122839
how many different equivalence relations
9651
Cardinality of cartesian product of an infinite set with N
65768
What is the cardinality of the set of the empty set?
16553
Cardinality of the set of all total orders on $\Bbb{N}$
68230
The cardinality of a countable union of sets with less than continuum cardinality
17935
Can a relation with less than 3 elements be considered transitive?
26569
Counting binary operations on a set with $n$ elements
12404
Union of definable sets
5215
Can the principle of inclusion/exclusion be used to count elements in the intersection of a sequence of sets?
111324
Finding number of relations on a set with 3 elements
144735
Possible cardinality of power sets