Count ordered arrangements of n distinct items taken all at once—the factorial n! formula
Count permutations of multiset objects when symbols repeat within fixed-length patterns
Count unordered k-subsets from n distinct items without replacement—the binomial n choose k
Count multisets of size k from n types when the same element may appear more than once
Count k-length ordered selections from n distinct items without reuse—the nPk partial permutation
Count k-length sequences from n symbols when each position may repeat any symbol (n^k cases)