OuLiPo, or Ouvroir de Littérature Potentielle (which they translate as “Charity bazaar of potential literature”) were a collection of writers I knew little about until yesterday. I knew a couple of things:

- Martin Gardner wrote about them, mentioning among other things that they had compiled a list of words which are both French and English words, so that one could write poems or prose with meaning in both languages (not necessarily the same).
- Georges Perec was associated with OuLiPo. He wrote a book,
*La Disparition*, not containing the letter E. This has been translated into English several times (obeying the same rule), most recently by my friend Julian West.

Clearly there is something about their word games which appeals to mathematicians!

I know much more now, thanks to an exposition “Oulipo, la littérature en jeu(x)” in the Bibliothèque de l’Arsenal in Paris. It is on until 15 February; go along if you can.

The first thing I learned was that two mathematicians were oulipiens: Claude Berge, the graph theorist whose Perfect Graph Conjecture tantalised us for so long, was a founding member in 1960; and Pierre Rosenstiehl, one of the triumvirate of editors-in-chief who set up the *European Journal of Combinatorics*, who joined in 1992. Yes, indeed, OuLiPo is still active. A very early amendment to the draft constitution states that one is an oulipien for eternity, though one may be “excused” on the grounds of death!

I was not so surprised by Berge’s involvement. I was aware that he had written a detective story where the solution of the problem involves graph theory, though I have not read it.

Other mathematical works (or should that be “plays”?) by oulipiens include *Les nombres remarquables* by founder François Le Lyonnais.

The exhibition catalogue devotes a page to “Mathématiques et Oulipo, de A à Z”. Reading it throws light on the relationship. Here are my rough translations of some entries:

G: Group, a mathematical structure in which, given two elements of the set, a third element is associated, respecting some constraints, of which the most celebrated is stated in *Princesse Hoppy …* by Jacques Roubaud [see below] under the name “rule of St Benoît”.

O: Oulipo, set of writers and mathematicians (defined by extension, that is, by a list of its elements). There is no law of composition, so Oulipo is not a group. And it is not a movement.

*Princess Hoppy …* is a short book without words, with illustrations looking like a cross between fairytale and playing cards. It was on show, and one could turn the pages; indeed, one was invited to discover the method of construction. Each page was an enlarged version of a section of the preceding page. In this way, the story was communicated. It also meant that one could work back from the final page (which was identical to the first page) and discover a tiny reduced image of the first page within itself. Hence the self-similarity, hence the group. But I never discovered what the “rule of St Benoît” states!

As to what Oulipo is, if not a group and not a movement, they say elsewhere “If Oulipo is a school, then it is a creche”; among other things, this captures their playful approach to literature, mathematics, games, and almost everything else.

In 1967, presumably following some discussion among oulipiens, Claude Berge wrote to Jacques Roubaud and Georges Perec, giving the example of a pair of orthogonal Latin squares of order 10, which had been found by Parker not long before (I described the context here). A copy of the letter is included in the exhibition. Perec was later to use these squares in the structure of perhaps his most famous book, *La Vie mode d’emploi* (loosely translated: “Life: A user’s manual”).

As well as Latin squares and graphs, they employed permutations and combinations. The mathematics page makes clear that the 12th century troubador Arnaut Daniel, inventor of the sestina, is an honorary olipien. (This link, or the Wikipedia page, describes the rather precise rules for a sestina, in which the pattern of word ends has a permutation applied to it as you move from each stanza to the next.) Raymond Queneau wrote a book *Cent mille milliards de poèmes* (10^{14} poems), where each page has a (14-line) sonnet, and the pages are cut between the lines so that any line can be taken from any sonnet to produce a poem.

Oulipo spun off several similar groupings, including ALAMO (Atelier de Littérature Assisté par la Mathématique et les Ordinateurs).

A final note: I don’t know for sure, but the title and cover of the Spanish translation of *La Disparition* suggested to me that this had been done so as to avoid the letter A. I have no idea whether this would be easier or harder than avoiding E in Spanish!

Was the immortal work of Louis D’Antin part of this movement? For example

Un petit d’un petit

S’étonne aux Halles

Un petit d’un petit

Ah! degrés te fallent

Indolent qui ne sort cesse

Indolent qui ne se mène

Qu’importe un petit d’un petit

Tout Gai de Reguennes.

See

http://www.aescon.com/aesconsulting/french/num1.htm

and there is a whole book in similar vein “Mots D’heures Gousses Rames”

http://www.abebooks.co.uk/book-search/title/mots-d'heures-gousses-rames-the-d'antin-manuscript/author/van-rooten-luis-d'antin/

Very much in their style, but not mentioned in the catalogue which claims to have a complete list of oulipiens et oulipiennes.

And in this 200th anniversary year of Waterloo, let us not forget Napoleon’s words as he boarded the British ship taking him to exile in St Helena: “Alors, c’est là.”