\column[yes]
\definemathfraction[binomial] setupmathfractions[binom] [fences=parenthesis,rule=no]\definemathfraction[tbinomial] [binomial] [mathstyle=text]\definemathfraction[dbinomial] [binomial] [mathstyle=display] \startbuffer\type{\binomial{n}{k}}: $\binomial{n}{k}$\par\type{\tbinomial{n}{k}}: $\tbinomial{n}{k}$\par\type{\dbinomial{n}{k}}: $\dbinomial{n}{k}$\par\stopbuffer
\switchtobodyfont[modern]
\stopcolumns
\stoptext
</context>
The result of the code above, with the standalone from 2017-09-05 is given below.
[[File:binomialcoefficients.png|700px]]
<context source="yes">
\startbuffer
\type{\binom{n}{k}}: $\binom{n}{k}$\par
\type{\tbinom{n}{k}}: $\tbinom{n}{k}$\par
\type{\dbinom{n}{k}}: $\dbinom{n}{k}$\par
\stopbuffer
\subsubject{Latin Modern} \getbuffer
\setupmathfractions[binomial][fences=parenthesis,threshold=1.5]
\subsubject{Latin Modern} \getbuffer
</context>