On Fri, Dec 07, 2018 at 12:04:44AM +0000, Raymond Hettinger wrote:

> Also, I'm not sure what the predominant choice for variable names 
> should be, "n things taken r at a time" or "n things taken k at time".
> 
> Also, it's worth considering whether the function should be called 
> "binomial", "choose", "combinations", or "comb".

I've done a quick survey of some of the most common/popular scientific 
calculators:

TI Nspire
TI-84 Plus
Casio Classpad
Casio FX-82AU Plus II

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.

For what its worth, the colour I prefer for this bikeshed are "comb" and 
"perm", which are the names used by the HP 48GX calculator. Second 
choice would be to spell the names out in full, "combinations" and 
"permutations".