C(n, m)-n is subscript, m is superscript (m is above c and n is below), and c (n, m) represents the number of combinations of n and m, which is equal to the product of m natural numbers decreasing continuously from n divided by the product of m natural numbers increasing continuously from 1.

Example:

C(8，3)=8*7*6/( 1*2*3) =56

A molecule is the product of three natural numbers that decrease continuously from 8.

The denominator is the product of three natural numbers that increase continuously from 1.

Extended data

1, combination definition

Combination is one of the important concepts in mathematics. Taking out M different elements (0≤m≤n) from N different elements at a time and synthesizing a group regardless of their order is called selecting the combination of M elements from N elements without repetition.

2. Total number of combinations

The total number of combinations is a positive integer, which means that 0, 1, 2, …, n different elements take the sum of all combinations of n different elements at a time.

3. Repeated combination

Combination with repetition is a special combination. You can repeatedly select m elements from n different elements. Synthesizing a group of m elements called n elements regardless of their order is a repeatable combination. Two repeated combinations are the same if and only if the elements are the same and the same elements are taken the same times.

References:

Baidu encyclopedia-combination