The alternative Sierpinski/ Riesel works off b^n+/-k. Numbers of this form have the same properties as k*b^n+/-1. (trust me, this is the case!!) It is not so popular because you cannot prove the numbers prime, only prp.

But there is a whole community of people out there interested in finding just that... numbers that are prp but not prime.

Check

http://www.primenumbers.net/prptop/prptop.php
Henri lists the top 10000 prps and therefore it is easy to get into this list.

But first you need to work out the probable Sierpinski/ Riesels for b^n+/-k, and then look at eliminating all k up to the chosen value. In this way you will find prps of some other k value such as L in b^n+/-L which Henri will be pleased to list