[seqfan] Ramanujan Prime chains

[John W. Nicholson]

In A168421 there is the following comment:

For some n and k, we see that a(n) = A104272(k) as to form a chain of primes similar to a Cunningham chain. For example (and the first example), a(2) = 7, links A104272(2) = 11 = a(3), links A104272(3) = 17 = a(4), links A104272(4) = 29 = a(6), links A104272(6) = 47. Note that the links do not have to be of a form like q = 2*p+1 or q = 2*p-1. - John W. Nicholson, Dec 14 2013

My question is: Does anyone see how to write a program which finds these chains fast? I use Pari/GP so code that would work with it would be great.

I think this is a bunch of sequences just dieing to be listed. And, there are some ideas in my head about them.

 
John W. Nicholson