But you aren't starting with pennies, you are starting with all the atoms in the universe from which you need to get very specific combinations. Calculate the probability of getting DNA from that.
That's looking at it from the wrong perspective it seems. We are not trying to get DNA. Not really trying to get anything.
IMHO the more reasonable question is "Given all the atoms in the universe what is the possibility that some might combine in a way that leads to replication?"
DNA is just one combination that did happen to work, one of several that we know about so far. There may well be other posibilities, ones we haven't even dreamed of, and there may well be ones that developed but were not as successful as DNA and so fell by the wayside.
But even the revised question is beyond our ability to frame or calculate. We just don't know all of the possibilities, or even all of the conditions possible.
What we do know is that the probability of DNA existing is 1.
Aslan is not a Tame Lion