Quote:
Originally Posted by Xentar
eh.. is it the same with
18 * 18^n+1 ?
and if not, could you please try to explain it to me? (Yea, I'm trying to learn the math behind these projects )

They are also just 18^n+1. Again, they can only be prime if n is a power of 2, and would be Generalised Fermat Numbers. Have a look at Yves Gallot's GFN page for more info.