Could never understand that equation Rick, and why some learned astronomer`s still quote it. It`s the Drake equation of course, but all he done, as you may know, was to guess at all the different types of stars, (of which there are a few billion), and the number of planet`s round them, (of which there may be billion`s), and how many may be habitable etc, and all done 50 years ago, before any extra-solar planet`s were even discovered. To me, and like many other`s, it is full of too much guess work, and no evidence whatsoever. Well done Rick for showing it. Now, E=Mc2.........
Incidently, Frank Drake is still alive and I am still a member of SETI, of which he is one of the founder`s.