@Steven D'Aprano:
> all call this nCr, and nPr for the permutation version. This matches 
> the notation taught in secondary school maths classes in Australia. 
> That's common and familiar notation for secondary school students, but 
> personally I'm not super-keen on it.

It's also not universal; in my experience, most calculators are localized for a given market, and may use different notations (in particular, the notation for combinations/binomial numbers changes across countries).