I've been trying to figure out something that should be simple but I seem
to be stuck. Perhaps someone can help. I need to figure out what the
probability of NOT finding a fragment which is r bp long in a sequence
which is n bp long. I can do this for individual cases but I need a
purely symbolic solution which would cover all cases. This is all
assuming a completely random sequence.
If anyone happens to know off the top of their heads what the solution is
it would be grotesquely appreciated.