[Jprogramming] Mathshallenge Repunits problems

[John Randall]

Richard Donovan wrote:
> Ref the latest two mathschallenge problems;
>
> They both relate to repunits.
>
> "A number consisting entirely of ones is called a repunit.
> We shall define R(k) to be a repunit of length k; for example, R(6) =
> 111111."
>
> I am having trouble creating large repunits as follows:
>

Minor spoiler follows.

























To solve these problems, you only have to determine

A(n)=min{k | n divides R(k)}.

Can you do this without actually generating R(k)?  Since A(n)>n, you are
going to have trouble doing the problems if you are trying to do divisions
of million-digit numbers.

Best wishes,

John