Permutations on the set of natural numbers.
122504
Factorisations of permutations
117862
Number of partitions of an $n$-element set into $k$ classes
41008
how many permutations of {1,2,...,9}
124890
Divisibility within a block of natural numbers
97254
What is the proof of permutations of similar objects?
136885
Series of natural numbers which has all same digits
39724
Combinatorial Identities
47720
Isomorphism from Natural numbers to the Odd Natural numbers
60416
Finding a permutation, and number of, from powers of the permutation
52861
Natural Numbers and Well ordering
44480
Let $\sigma :\{1,2,3,4,5\} \rightarrow \{1,2,3,4,5\}$ be permutations such that $ \sigma^{-1}(j) \leq \sigma(j)~\forall j, 1 \leq j \leq 5$.
85023
Permutation of n objects with restriction of adjacent pairs
147766
Sum of Permutations from 0 to n
103106
Proving that any permutation in $S_n$ can be written as a product of disjoint cycles
74730
Combinatorial Proof of ${{n}\choose{k}} {{k}\choose{j}} = {{n}\choose{j}} {{n-j}\choose{k-j}}$
77171
How to find unique multisets of n naturals of a given domain and their numbers?
148413
Proving $S_n$ is generated by the set $\{(1\text{ }2),(2\text{ }3),\cdots,(n-1\text{ }n)\}$ of $n-1$ transpositions.