Arrange $n$ people so that some people are never together.
85023
Permutation of n objects with restriction of adjacent pairs
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?
147901
Show that, in a group of n people, everyone has the same number of friends if..
84910
Generate some number of lists of pairs given a list of people
100495
Expected number of siblings, given the expectation of children in a family
62102
Probability that n people collectively occupy all 365 birthdays
59419
Crafty solutions to the following limit
83736
The probability that no person has the same birthday month
124290
Shuffle list, ensuring that no item remains in same position
69827
Set conditions at a permutation
118007
Not lifting your pen on the $n\times n$ grid
72874
GCSE: Find the number of person that will go to a party
81505
Derangement of $n$ elements
96086
Double Factorial: Number of possibilities to partition a set of $2n$ items into $n$ pairs
134888
Ethical ways to dissuade?
83841
Mutual Exclusion Problem
57644
Lower bounds for ${{2n} \choose {n}}$