# MathBinomialCoefficient Calculates the binomial coefficient: C(n,k)=n!/(k!*(n-k)!). ``` long  MathBinomialCoefficient(    const int  n,      // the total number of elements    const int  k       // the number of elements in combination    ) ``` Parameters n [in] The number of elements. k [in] The number of elements for each combination. Return Value The number of combinations of N choose K.