According to Goran, the function nChooseKis part of R.basic. You can talk about this in the above example by looking at the top of the page:

"R.basic" , , "R.basic". nChooseK
library(R.basic)
R.basic,
install.packages("R.basic", contriburl="http://www.braju.com/R/repos/")
library(R.basic)
, choose R
choose(37, 12)
nChooseK(37, 12)