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HMMT November 2019 U32

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A sequence of real numbers a0,a1,…,a9a_{0}, a_{1}, \ldots, a_{9} with a0=0,a1=1a_{0}=0, a_{1}=1, and a2>0a_{2}>0 satisfies

an+2anan−1=an+2+an+an−1a_{n+2} a_{n} a_{n-1}=a_{n+2}+a_{n}+a_{n-1}

for all 1≤n≤71 \leq n \leq 7, but cannot be extended to a10a_{10}. In other words, no values of a10∈Ra_{10} \in \mathbb{R} satisfy

a10a8a7=a10+a8+a7a_{10} a_{8} a_{7}=a_{10}+a_{8}+a_{7}

Compute the smallest possible value of a2a_{2}.

Dataset text NuminaMath olympiads. Quoted with source.

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\sqrt{2}-1

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