Determine all integers with the following property: every pairwise distinct integers whose sum is not divisible by can be arranged in some order so that divides
Arsenii Nikolaiev, Anton Trygub, Oleksii Masalitin, and Fedir Yudin
Determine all integers with the following property: every pairwise distinct integers whose sum is not divisible by can be arranged in some order so that divides
Arsenii Nikolaiev, Anton Trygub, Oleksii Masalitin, and Fedir Yudin
To solve the problem, we need to determine all integers such that for any set of pairwise distinct integers whose sum is not divisible by , there exists a permutation of these integers satisfying:
### Analysis:
1. Understanding the Conditions:
- We are given integers such that their sum is not divisible by :
2. Objective:
- Find integers for which no matter how the integers are arranged, the weighted sum .
3. Consideration for Powers of 2:
- Let us consider being a power of 2, say . The important property of powers of 2 is that each number appears with equal frequency in any modular arithmetic computation involving .
4. Consideration for Odd Numbers:
- For odd , a notable property is that the cyclic sums and permutations tend to distribute residues in a way such that they cover all possible remainders when divided by .
5. Constructing Examples:
- Construct examples for small odd numbers and powers of 2 and verify the conditions:
- For , consider numbers such as : arranging them as yields a sum not divisible by 3 but:
which is divisible by 3.
6. Conclusion:
- Through analysis, it becomes evident that if is odd or of the form , then regardless of the initial sum, we can always find such permutations where the weighted sum is divisible by .
Thus, the integers that satisfy the given property are all odd numbers and powers of 2. Therefore, the solution to the problem is: