Let $a, b, c$ be positive integers. Define the sequence $u_n$: $$u_n = a \cdot 2^n + b \cdot 5^n + c$$ Show that there exists infinitely many $n$ such that $u_n$ is not a perfect square.
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2025-01-13 02:39:54.1736735994
Show that there exists infinitely many $n$ such that $u_n$ is not a perfect square
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