If k is rational power of base (b), then .... (let k = b^(r/s) with gcd(r,s) = 1)
* For the Riesel case, this is generalized repunit number to base b^(1/s)
* For the Sierpinski case, if s is odd, then this is generalized (half) Fermat number to base b^(1/s)
* For the Sierpinski case, if s is even, then this is generalized repunit number to negative base b^(1/s)
