Reflexive relation on set of $n$ elements
1643
Number of reflexive relations defined on a set A with n elements
142718
How can I find the smallest set of groups of $n$ elements such that every element is in the same group as every other at least once?
61747
Proof of exchange principle in set theory
57221
counting the number of elements in a conjugacy class of $S_n$
130771
Sets and the principle of inclusion and exclusion
1409
Proving that the given set has at most $2^{n-1}$ elements
103769
The Cartesian product of a finite number of countable sets is countable
3392
Sum of products of elements of nonempty subsets of A set
85852
How many total order relations on a set $A$?
37331
Prove that every set with more than one element has a permutation without fixed points
3465
Equivalence relations and power sets.
75966
Prove that if $A$ is a set with $m$ elements, $B$ is a set with $n$ elements, and $A \cap B = \emptyset$, then $A \cup B$ has $m+n$ elements.
77337
Is an Anti-Symmetric Relation also Reflexive?
148399
Two sets which contain each other as elements
138436
How to prove reflexivity, symmetry and transitivity for the following relation?
82169
Why does a partially ordered set need to be reflexive?
143060
If a relation is symmetric and transitive, will it be reflexive?