Higher Derivatives of the Falling Factorial and Related Generalizations   of the Stirling and Harmonic Numbers
  Through a brute-force approach to calculating the higher derivatives of the falling factorial function, a number of interesting quantities were obtained and analyzed. In particular, it was found that a quantity that can be described as the "elementary symmetric harmonic sum" is a natural way to describe the solutions to such higher derivatives. The relationship of this type of generalized harmonic number to other quantities discussed in the literature, such as the r-Stirling numbers, was described in detail. 
Steven S. Poon
math.CO