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MathNet 2022-part-02 — 197 problems (EN–VI) Question 3

Math Olympiad Vault · MathNet 2022-part-02 — 197 problems (EN–VI)

Question 3

Consider an infinite sequence $a_0, a_1, a_2, \dots$ of integers that satisfies
$$
a_0 \ge 1 \quad \text{and} \quad a_{n+1} \in \{2022a_n - 1, 2022a_n + 1\}
$$
for all indices $n \ge 0$. Prove that any such infinite sequence contains infinitely many composite numbers.
(Martin Melicher)