Calculation process: The calculation formula of known combination number is shown in the following figure:

The specific calculation is shown in the following figure:

Extended data:

1, combination is one of the important concepts in mathematics. Taking out m different elements from n different elements at a time, regardless of the order, is called choosing the combination of m elements from n elements without repetition. The number of species in all such combinations is called the combination number.

2. The factorial of positive integers is the product of all positive integers less than or equal to this number, and the factorial of 0 is 1. The factorial writing of natural number n! . In 1808, Keyston Kaman introduced this symbol. Which is n! =1× 2× 3× ...× n. The factor can also be defined recursively: 0! = 1，n！ =(n- 1)！ ×n .

References:

Baidu Encyclopedia _ Combination Number