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MathNet 2019-part-01 — 184 problems (EN–VI) Question 101

Math Olympiad Vault · MathNet 2019-part-01 — 184 problems (EN–VI)

Question 101

Let the odd positive integer $a$ not be a perfect square, let $b$ and $c$ be odd primes, and
$$
a^2 + a + 1 = 3(b^2 + b + 1)(c^2 + c + 1).
$$
Prove that at least one of $b^2 + b + 1$ and $c^2 + c + 1$ is composite.