A combination is a selection of items from a set that has distinct members, such that the order of selection does not matter. Unlike permutations.
A k-combination of a set is a subset of that has distinct elements of
in other words, if a set has elements and we need to select of them and we do not care about the order, is the number of k-combinations, and is also a binomial coefficient - that is, one of the numbers seen in Pascal’s triangle.
A k-combination can be represented in one of these ways.
Symmetry seen in Pascal’s triangle is represented with the equation .
a special case of the combination function where can use the formula