The number of sets satisfying that the sum of elements is equal to the product of elements If a set element belongs to a positive integer, find the number of all sets that satisfy that the sum of elements is equal to the product of elements
When there is no 1 in the element, the smallest element is 2. Let a belong to a
2a=a+a>a+2
Therefore, the set must contain 1
If the set contains four or more elements, it is denoted as n
You can see that there are at most three elements
There can't be two elements
Therefore, only 1 + 2 + 3 = 1 * 2 * 3 is consistent
The number of all sets whose sum of elements is equal to the product of elements is 1