@Randal'Thor @GentlePurpleRain Thank you both for clarifying. And I too am grateful that we have Rand back & contributing. But as for focusing on the present, those who cannot remember the past are condemned to repeat it, as George Santayana said.

I might be wrong, but doesn't this sound like a standard textbook-style counting problem?

@RosieF True, but when the past is confidential, there's not a lot that others can learn from it, unfortunately.

@Ankoganit You are not wrong.

@Ankoganit Yes, it does seem on the face of it that there won't be an aha! moment -- it seems to be a mundane combinatorics problem. Not that there aren't any beautiful results in combinatorics -- there are -- but this doesn't look as if it's one of them.