How many routes from $(0,0)$ to $(2n,2n)$ avoiding $(2k+1,2k+1)$?
92554
How many lattice paths are there from $(0,0)$ to $(2n,2n)$ that avoids odd points
35515
Find the number of $(m+n)$ digit binary sequences with $m$ $0$'s and $n$ $1$'s such that no two $1$'s are adjacent
68882
Path to Combinatorics Problem [$1.11$]
69833
Number of elements not equal to their inverses is even number
140416
Catalan number - combinatoric
9411
Number of permutations of $n$ elements where no number $i$ is in position $i$
58508
Number of ways to pair off $2n$ points such that no chords intersect
22869
Prove $[0, 1]$ and $(0, 1]$ are equinumerous by use of bijection
142307
Counting invertible $0$-$1$ matrices that remain invertible under negating the diagonal
34452
In how many ways can you choose $k$ numbers out of $\{1,2,3,\dots,n\}$ so none of them is consecutive?
42706
How many $N$ digits binary numbers can be formed where $0$ is not repeated
149609
Conditions on cycle types for permutations to generate $S_n$
45216
Cardinality of $[0,1]$
32039
What are the trailing number of the zeroes in the given integer
6204
How many permutations of $\{1, \ldots, n\}$ exist such that none of them contain $(i, i+1)$ (as a sequence) for $i \in {1,...,(n-1)}$?
46971
Number of surjections from $\{1,...,m\}$ to $\{1,...,n\}$
156383
Proving a combinatorial identity without double counting