Binomial coefficients with Mathcad 8.0?

The function you are looking for is combin(n,k) for "n over k"

https://support.ptc.com/help/mathcad/r8.0/en/index.html#page/PTC_Mathcad_Help/combinations_and_permutations.html#

Example:

If you want to create your own  function, you must take care which definition to use, because factorials and Gamma function may easily exceed the limit of 10^307 and throw an error.