Thank you for doing the math, Oli. People(mostly musician/composers suffering from chronic depression) drag out the old line about "there are only twelve notes. All the melodies have been written already" a lot, and this gives me a comprehensive answer that I can email or text.
It's a big help, because I tend to sit the offender in a chair while I play out all the two, three , and four note possibilities I can think of. They usually run screaming from the room at some point, and I collapse from nervous exhaustion. A bad business, all around, really, and this saves all that.