P1891 Crazy LCM
Background
As we all know, czmppppp is a math genius. One day, he gave the newbies a number theory problem, and they were all shocked.
Description
Given $n$, compute
$$\sum_{i = 1}^n \operatorname{lcm}(i, n)$$
where $\operatorname{lcm}(i, j)$ denotes the least common multiple of $i$ and $j$.
Input Format
**There are multiple test cases in a single test point.**
The first line contains an integer $T$, the number of test cases.
The next $T$ lines each contain one integer $n$.
Output Format
For each test case, output one line with a single integer representing the answer.
Explanation/Hint
- Constraints:
- For $30\%$ of the testdata, $T \leq 5$, $n \leq 10^5$.
- For $100\%$ of the testdata, $1 \leq T \leq 3 \times 10^5$, $1 \leq n \leq 10^6$.
Translated by ChatGPT 5