code: private BigInteger computeNfactdivkNkFact(final int n,
                                                final int k)
      {
          final int nminusk = n - k;
  
          BigInteger kfactTimesnmkfact = factorial(k).multiply(factorial(nminusk));
          BigInteger nfactorial = factorial(n);
  
          return nfactorial.divide(kfactTimesnmkfact);
      }
docs: Return (n!) / ( k! * (n-k)! ).
  
  @param n
  @param k
  @return value from equation above