Claude Berge and the “ Oulipo ”

is well-known in the Operational Research community for his path-breaking contributions to graph theory. He received several awards for his scientific achievements, including the EURO Gold Medal (1989) and the Euler Prize (1995, jointly with R.L. Graham). The name of Claude Berge is likely to remain in history for several other reasons. For instance he was an expert in the Asmat art from New-Guinea. He was himself a famous sculptor. We would like here to mention yet another facet of Claude Berge. He was a founding member of Oulipo (for " OUvroir de LIttérature POtentielle " , i.e., " workroom of potential literature "). This group was created on 24 November 1960 under the impulsion of Raymond Queneau and François Le Lionnais (the other founding members were Albert-they were joined later by several well-known members including Italo Calvino, Harry Mattews, Georges Perec and Jacques Roubaud). Oulipo was a group of writers and mathematicians aiming at exploring in a systematic way formal constraints on the production of literary texts. Although poets had explored for years the formal constraints of versification, the originality of the group was to develop new or rarely studied constraints and to explore them systematically. With this objective in mind, the collaboration between writers and mathematicians proved extremely useful and Oulipo is considered to be among the most influential literary groups in France in the twentieth century. The group is still active today. According to the rules of the group, Claude Berge will be " excusé pour cause de décès " at each meeting of Oulipo. It is impossible here to give a complete overview of the incredible variety of constraints that the members of the group have explored and are still exploring. It is nevertheless quite certain that Claude Berge has participated in the development and study of many of them besides producing his own texts. Georges Perec was perhaps one of the most talented and prolific member of Oulipo. In his book La Vie, mode d'emploi [12], Perec tells a story happening in a building of ten floors with ten rooms in each floor, based on the rather recent (at that time) discovery of orthogonal Latin squares of size 10: it is a 10 by 10 array in each entry of which we have one of the numbers 1 to 10 and one letter a, b, c, ..., h, i, j; these are arranged in such …