Determine all composite positive integers with the following property: If are all the positive divisors of , then
(Walther Janous)
Determine all composite positive integers with the following property: If are all the positive divisors of , then
(Walther Janous)
To determine all composite positive integers with the given property, we need to analyze the sequence of divisors and their differences. Let's break down the problem step by step.
1. Identify the divisors and their differences:
Let be all the positive divisors of . The given property states that:
This means:
2. **Express the divisors in terms of :**
Since and , we have . Similarly, implies , and so on. We can generalize this pattern:
For example:
However, this pattern does not hold for all . Instead, we need to find a consistent pattern that fits the given ratio.
3. **Analyze the pattern for small values of :**
Let's consider small values of to find a consistent pattern:
- For :
The differences are:
This matches the ratio .
4. **Verify if is a solution:**
For , the divisors are . The differences are:
This matches the ratio .
5. **Check for larger values of :**
If , the pattern for each integer does not hold because the differences would not be equal to 1. Therefore, cannot be greater than 3.
6. Conclusion:
The only composite positive integer that satisfies the given property is .
The final answer is .