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MathNet 2015-part-07 — 185 problems (EN–VI) Question 177

Math Olympiad Vault · MathNet 2015-part-07 — 185 problems (EN–VI)

Question 177

For positive integers $a$, $n$; consider the following equation:
$$
a^2x + 6a y + 36z = n
$$
where $x$, $y$, $z$ are non-negative natural numbers.

a) Find all integers $a$ such that for all $n \ge 250$, the given equation always has natural roots $(x, y, z)$.

b) Given that $a \gt 1$ and $\gcd(a, 6) = 1$. Find the greatest value of $n$ in terms of $a$ such that the given equation doesn't have natural root $(x, y, z)$.