MathDB

Let a_0,a_1,\dots,a_{n \plus{} 1} be natural numbers such that a_0 \equal{} a_{n \plus{} 1} \equal{} 1,

a_i>1

for all

1\leq i \leq n

, and for each

1\leq j\leq n

, a_i|a_{i \minus{} 1} \plus{} a_{i \plus{} 1}. Prove that there exist one

2

in the sequence.

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