Problem 52 (difficulty: 6/10)

Let \(\displaystyle u_n\) be the \(\displaystyle n\)-th Fibonacci number (\(\displaystyle u_0=0\), \(\displaystyle u_1=1\), \(\displaystyle u_2=1\), \(\displaystyle u_3=2\), \(\displaystyle u_4=3\), \(\displaystyle u_5=5\), \(\displaystyle u_6=8\),

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