P104
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Pandigital Fibonacci Ends

ℹ️Published on Friday, 9th September 2005, 06:00 pm; Solved by 17906;
Difficulty rating: 25%

The Fibonacci sequence is defined by the recurrence relation:

$F_n = F_{n - 1} + F_{n - 2}$, where $F_1 = 1$ and $F_2 = 1$.

It turns out that $F_{541}$, which contains $113$ digits, is the first Fibonacci number for which the last nine digits are $1$-$9$ pandigital (contain all the digits $1$ to $9$, but not necessarily in order). And $F_{2749}$, which contains $575$ digits, is the first Fibonacci number for which the first nine digits are $1$-$9$ pandigital.

Given that $F_k$ is the first Fibonacci number for which the first nine digits AND the last nine digits are $1$-$9$ pandigital, find $k$.



Soluzione

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