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Problem 104


Problem 104


Pandigital Fibonacci ends

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 $k$.


两端全数字的斐波那契数

斐波那契数列由如下递归关系生成:
$F_n=F_{n-1}+F_{n-2}$,其中$F_1=1$,且$F_2=1$。

包含有$113$位数字的$F_{541}$是第一个最后$9$位数字是$1$至$9$全数字(包含$1$至$9$所有的数字,但不一定按照顺序)的斐波那契数,而包含有$575$位数字的$F_{2749}$是第一个前$9$位数字是$1$至$9$全数字的斐波那契数。

若$F_k$是第一个前$9$位数字和后$9$位数字都是$1$至$9$全数字的斐波那契数,求$k$。