Lah numbers and Laguerre polynomials of order negative one
  In this article we point out interesting connections among Lah numbers, Laguerre polynomials of order negative one, and exponential polynomials. We also discuss several different expressions for the higher order derivatives of exp (1/x). A new representation of these derivatives is given in terms of exponential polynomials 
Khristo N. Boyadzhiev (Department of Mathematics and Statistics, Ohio   Northern University, Ada, OH)
math.NT