Preparando MOJI
Mr. Chanek has an array $$$a$$$ of $$$n$$$ integers. The prettiness value of $$$a$$$ is denoted as:
$$$$$$\sum_{i=1}^{n} {\sum_{j=1}^{n} {\gcd(a_i, a_j) \cdot \gcd(i, j)}}$$$$$$
where $$$\gcd(x, y)$$$ denotes the greatest common divisor (GCD) of integers $$$x$$$ and $$$y$$$.
In other words, the prettiness value of an array $$$a$$$ is the total sum of $$$\gcd(a_i, a_j) \cdot \gcd(i, j)$$$ for all pairs $$$(i, j)$$$.
Help Mr. Chanek find the prettiness value of $$$a$$$, and output the result modulo $$$10^9 + 7$$$!
The first line contains an integer $$$n$$$ ($$$2 \leq n \leq 10^5$$$).
The second line contains $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \leq a_i \leq 10^5$$$).
Output an integer denoting the prettiness value of $$$a$$$ modulo $$$10^9 + 7$$$.
5 3 6 2 1 4
77
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Provedor Codeforces
Código CF1575G
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Datas 09/05/2023 10:17:51
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