The first Fibonacci numbers are: .
It can be seen that and are not squarefree: is divisible by and is divisible by and by .
So the first squarefree Fibonacci numbers are: and .
The th squarefree Fibonacci number is:
.
The last sixteen digits of this number are: and in scientific notation this number can be written as .
Find the th squarefree Fibonacci number.
Give as your answer its last sixteen digits followed by a comma followed by the number in scientific notation (rounded to one digit after the decimal point).
For the th squarefree number the answer would have been: 1608739584170445,9.7e53
Note:
For this problem, assume that for every prime , the first fibonacci number divisible by is not divisible by (this is part of Wall's conjecture). This has been verified for primes , but has not been proven in general.
If it happens that the conjecture is false, then the accepted answer to this problem isn't guaranteed to be the th squarefree Fibonacci number, rather it represents only a lower bound for that number.
Write-up coming later
The complete problem is available here. An approach, code, and answer will be added later.