Number of ways to select $m$ items out of $k$ categories, where each category is selected at least once and selection order matters?
52348
Counting the number of surjections.
34452
In how many ways can you choose $k$ numbers out of $\{1,2,3,\dots,n\}$ so none of them is consecutive?
136037
${n\choose 2} - {k\choose 2} = {n-k\choose 2} +k(n-k)$ Marked box or unmarked box
24312
Choosing optimal K for KNN
53179
Combinations, when placing n objects into k boxes, each box has its own size and the order in them doesn't matter?
74730
Combinatorial Proof of ${{n}\choose{k}} {{k}\choose{j}} = {{n}\choose{j}} {{n-j}\choose{k-j}}$
21929
A cleaner way to select by multiple possible attribute values?
142534
Proof of $k {n\choose k} = n {n-1 \choose k-1}$ using direct proof
70637
Selecting items in a list based on multiple conditions
76405
Let n be an even integer. How many different ways can I choose subsets of the set {1,2...,n}
88356
Number of options to distribute $N$ different balls to $K$ numbered cells
11876
Probability of complete coupon set in $K$ boxes where a box has $N$ distinct coupons?
43821
MS excel - assigning "categories" based on keywords
117025
Selection algorithms on sorted matrix
97111
Weighted choice short and simple
97314
Counting nearly-sorted permutations
105146
$M$ contains all ordinals