Small Octos
I've been looking at the small bases. (primes, rather than probable primes) I wrote my own program to look at these.
There are no octoproths with base n = 26 or below.
The first one is
109989075 27
and is the only one with base 27.
The next are
21207165 28
191093475 28
are the only two with base 28.
...more to come
One interesting one is n=1, k=15.
15*2^1+1 = 31
15*2^11 = 29
15*2^(1+1)+1 = 61
15*2^(1+1)1 = 59
2^1+15 = 17
2^115 = 13
2^(1+1)+15 = 19
2^(1+1)15 = 11
If you count negative primes too.
