IMO Shortlist 2017 problem A4


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Oct. 3, 2019
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A sequence of real numbers a_1,a_2,\ldots satisfies the relation a_n=-\max_{i+j=n}(a_i+a_j)\qquad\text{for all}\quad n>2017.Prove that the sequence is bounded, i.e., there is a constant M such that |a_n|\leq M for all positive integers n.

Source: https://www.imo-official.org/problems/IMO2017SL.pdf