Hope everyone can give me some suggestions to solve this problem

Revision en6, by hgtfrdeswa, 2024-10-08 15:07:01

Given a sequence of integers $$$( a_1, a_2, \dots, a_n )$$$ where $$$( 1 \leq a_i \leq 10^6 )$$$, count the number of subsequences with indices $$$( i_1, i_2, \dots, i_k )$$$ such that: \begin{itemize} \item $$$ k > 0 $$$, \item $$$ 1 < i_2 < \dots < i_k \leq n ,$$$ \item $$$ a_{i_1} \leq a_{i_2} \leq \dots \leq a_{i_k} ,$$$ \item $$$ \gcd(a_{i_1}, a_{i_2}, \dots, a_{i_k}) = 1 .$$$ \end{itemize} \begin{itemize} \item The first line contains an integer $$$n $$$ $$$(1 \leq n \leq 3 \times 10^5)$$$, representing the number of elements in the sequence. \item The second line contains $$$ n $$$ integers $$$ a_1, a_2, \dots, a_n $$$ $$$(1 \leq a_i \leq 10^6)$$$. \end{itemize}

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