Philippe Flajolet does research in enumerative and asymptotic combinatorics as well as probabilistic analysis of algorithms in computer science. he is the coauthor with Robert Sedgewick of the book ANALYTIC COMBINATORICS of which a free copy can be downloaded from the site http://algo.inria.fr/flajolet/, which contains about 100 publications, mostly dealing with discrete mathematics.
Philippe Flajolet died suddenly on March 22, 2011. The page http://algo.inria.fr/flajolet/ will be left untouched.
Wikipedia: Philippe Flajolet