Given the problem, we are tasked with finding all integers n≥2 such that there exists a permutation x0,x1,…,xn−1 of the numbers 0,1,…,n−1 with the property that the n numbers
x0,x0+x1,…,x0+x1+…+xn−1
are pairwise distinct modulo n.
To solve this, consider the sequence Sk=x0+x1+…+xk for 0≤k<n. We need S0,S1,…,Sn−1 to be distinct modulo n.
### Step 1: Permutation and Constraints
Since x0,x1,…,xn−1 is a permutation of 0,1,…,n−1, we have:
x0+x1+…+xn−1≡0+1+…+(n−1)≡2n(n−1)(modn)
This reduces to:
x0+x1+…+xn−1≡0(modn)
Thus, Sn−1≡0(modn).
### Step 2: Distinctness Condition
For S0,S1,…,Sn−1 to be pairwise distinct modulo n, we need:
Sk1≡Sk2(modn)for0≤k1<k2<n
### Step 3: Consider Special Cases
- **Case n=2:** The permutation (0,1) works because:
S0=0,S1=0+1=1
Both are distinct modulo 2.
- **Even n≥2:** Consider the permutation that results in distinct cumulative sums. By constructing carefully, we can ensure the sums are distinct modulo n.
- **Odd n:** If n is odd, consider:
Sk≡Sk′(modn)for some k<k′ since n∣2n(n−1)
Since 2n(n−1) is an integer and n odd, this leads to a contradiction of the distinct condition.
### Conclusion
Thus, the integer n must be even for the condition to hold. Therefore, the solution is:
even integers n≥2
This concludes that all even integers greater than or equal to 2 satisfy the given property in the problem.