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Problem 886

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Coprime Permutations

A permutation of $\{2,3,\ldots,n\}$ is a rearrangement of these numbers. A coprime permutation is a rearrangement such that all pairs of adjacent numbers are coprime.

Let $P(n)$ be the number of coprime permutations of $\{2,3,\ldots,n\}$.

For example, $P(4)=2$ as there are two coprime permutations, $(2,3,4)$ and $(4,3,2)$. You are also given $P(10)=576$.

Find $P(34)$ and give your answer modulo $83\ 456\ 729$.

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互质重排

$\{2,3,\ldots,n\}$的重排是将该集合中的所有数重新排列所得的结果，而互质重排则是相邻两数总是互质的重排。

记$P(n)$为$\{2,3,\ldots,n\}$的所有互质重排的数目。

例如，$P(4)=2$，即存在两种互质重排，分别是$(2,3,4)$和$(4,3,2)$。此外还已知$P(10)=576$。

求$P(34)$，并对$83\ 456\ 729$取余作为你的答案。

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