A Simple Proof of an Identity of Lacasse Yidong Sun DOI: https://doi.org/10.37236/3032 Keywords: Derangement polynomial, Umbral operator. Abstract In this note, using the derangement polynomials and their umbral representation, we give another simple proof of an identity conjectured by Lacasse in the study of the PAC-Bayesian machine learning theory. PDF Published 2013-04-17 Issue Volume 20, Issue 2 (2013) Article Number P11