Monatsh Math (2008) 155:213–215 DOI 10.1007/s00605-008-0007-9 Journées de Numération, Graz University of Technology, April 16–20, 2007 Pierre Arnoux · Guy Barat · Peter J. Grabner · Jörg M. Thuswaldner Published online: 7 August 2008 © Springer-Verlag 2008 Combinatorics on words, geometrical theory of substitutions, fractal tilings, formal languages, digital expansions, quasi-crystals, Pisot and Salem numbers, and combina- torial game theory are active areas of research. During the last 10 years there has been an impulse from various groups, which found a common interest in these topics. These groups coming from diverse fields such as theoretical computer science, theoretical physics, discrete mathematics, dynamical system, and number theory decided to have regular meetings, which are organised under the title “Journées de Numération”. After some informal meetings in Marseille larger international meetings started in 2005 in Grenoble. The conference in Graz 2007 finds a continuation in Prague 2008. Such meetings would not have been possible without the generous support from national funding organisations: the French side was supported as an ACI “Nouvelles interfaces des Mathématiques”, the Austrian side is funded by the Austrian Science Foundation (FWF) as a national research network “Analytic Combinatorics and Prob- abilistic Number Theory”. The conference in Graz was also supported by the town of Graz, the local government of Styria, and Graz University of Technology. P. Arnoux Equipe Dynamique, Arithmétique et Combinatoire Institut de Mathématique de Luminy, CNRS UPR 9016 163, avenue de Luminy, Case 907, 13288 Marseille cedex 09, France e-mail: arnoux@iml.univ-mrs.fr G. Barat (B ) · P. J. Grabner Technische Universität Graz, Institut für Analysis und Computational Number Theory (Math A), Steyrergasse 30/II, 8010 Graz, Austria e-mail: guy.barat@tugraz.at J. M. Thuswaldner Department Mathematik und Informations Technologie, Franz Josef Straße 18, 8700 Leoben, Austria e-mail: joerg.thuswaldner@unileoben.ac.at 123