Each time you search, you iterate a potential factor from a new start to the square root of n. In order to avoid duplicate, the new start should be larger than the factor you previously divide n by.

```
public class Solution {
public List<List<Integer>> getFactors(int n) {
List<List<Integer>> result = new ArrayList<>();
search(result, new ArrayList<Integer>(), 2, n);
return result;
}
private void search(List<List<Integer>> result, List<Integer> currList, int floor, int number) {
for (int i = floor; i <= Math.sqrt(number); i++) {
if (number % i == 0) {
currList.add(i);
search(result, currList, i, number / i);
currList.add(number / i);
result.add(new ArrayList<>(currList));
currList.remove(currList.size() - 1);
currList.remove(currList.size() - 1);
}
}
}
}
```