> Write a function per(n) which returns the periodicity of 1/n, i.e.
> =A0 per(3) =3D> 1
> =A0 per(4) =3D> 0
> =A0 per(7) =3D> 6
> =A0 per(11) =3D> 2

I think you're going to have to explain what periodicity is, or
provide a link... I've no clue.