

The biggest hits at the Jaipur Literature Festival are often the people you had never heard of before. Even as the celebrated American novelist Jonathan Franzen was being ushered off one of the venue's larger stages, organizers at the smallest of the stages saw they had seriously underestimated the popularity of its theme: prime numbers.



One part grown-ups with biographies of Srinivasa Ramanujan sticking out of their backpacks and several parts school children bussed in from all over Rajasthan, the audience was there to hear Marcus Du Sautoy (pronounced so-toy), Charles Simonyi Professor for the Public Understanding of Science at the University of Oxford.



Du Sautoy's webpage notes apologetically: "Unfortunately my waiting list for school visits is now full so I can't accept anymore invitations to talk to schools at the moment." His popularity on the schools circuit is no surprise. He is a respected mathematician much lauded by his academic peers for his talents as a communicator to non-specialist audiences. He is a veteran of BBC documentaries, writes a regular column ("Sexy Science") for The Times and is a regular contributor to the Guardian, explaining the properties of large numbers one week and debunking myths about the dressing habits of mathematicians the next.



Bald head shining out of a salmon-pink shirt, Du Sautoy brought to his Jaipur appearances a chatty enthusiasm for his subject matter quite different from the bristly and confrontational ways of his better-known predecessor in that Chair, Richard Dawkins. Mathematics, he said, was about looking for patterns, and offered his audience some mathematical patterns to chew on. 2, 3, 5, 7, 11, 13... what is the next number in that series? 17 the audience called out, needing no help in spotting that this was the series of prime numbers - numbers evenly divisible only by themselves and one. This took him to his big subject: the apparent impossibility of finding a formula that will reliably predict where the next prime number is to be found.



'I've always wanted a prime for a phone number', he said winningly, as he proceeded to talk his audience - median age 15 - through the cutting edge of mathematical research on primes. 'It's such a shame', he said, 'that so much maths teaching is like piano teaching, months of practising scales and arpeggios and never getting to play any actual music.'



Elevated to the Festival's largest venue the next evening, he took on a bigger subject still: symmetry. This subject proved just the thing for an audience still waiting to be shown why a mathematician belonged at a festival of literature. A few minutes of intellectual autobiography set the scene: the young Du Sautoy gave up his childish ambitions of espionage after he found the Russian language too irregular for his tastes, and finding the order he sought in the language of mathematics. But lest anyone thought him some sort of idiot savant, he protested that the appeal of mathematics lay in its surprises.



Several surprises followed for the audience, who were led through the elementary theory of symmetry but quickly graduated from practising their scales to getting, quite literally, to the music. The familiar chords of Bach's Goldberg Variations played as backdrop to a commentary on the great composer's sensitivity to mathematical patterns, and the boldness with which the patterns were, every so often, disrupted.



Next it was the turn of the Alhambra, that masterpiece of Spanish architecture, to be given the Du Sautoy treatment. Its every tile, he pointed out, exemplified "a different symmetry", illustrating the point with photographs from what he called, with disarming geekiness, a "mathematical family holiday". Richard Dawkins, in his 2012 appearance at the festival, found his feet among a line-up of poets and novelists with a poetic turn of phrase and a sense of the provocativeness of his claims about modern genetics. Du Sautoy on the other hand looked to earn his keep at a festival of the humanities by articulating a vision of mathematics as a humanistic discipline whose practitioners are sensitive to beauty and motivated in their researches by the same mysterious inner necessities that move the artist.



He had judged his audience well. There were the obligatory expressions of gratitude to the ancient Indians who invented the zero and may well have anticipated the contributions of the 13th-century Italian Leonardo Fibonacci. Indian audiences now expect these ritual invocations of their country's past glories even while their best mathematical minds are regularly drawn away from the serious study of pure mathematics. The questions from the audience gave no evidence that India's mathematical glories were anything but past.



Dan Brown was the tutelary deity of the early questioners, calling on Du Sautoy's considerable stores of English tact to point out it was possible to see patterns where there were none to be found. What are your views on numerology, asked another. A sign of the natural human impulse to look for meaning in patterns, he said. A healthy impulse when it's twinned with our equally natural critical faculties that help us tell the genuine patterns from the mere "noise". It didn't feel like a putdown, but there was no sign that he would be lowering his standards out of a desire to be nice.



Whither the mathematical amateur, asked a third. Was mathematics a professional's game now? This was the cue for a little spiel on the fabled GH Hardy - Ramanujan friendship and an admission that there would always be room for genius and intuition in the discipline, though that genius might need some help formulating its proofs in the approved formal language. There was a furrow on Du Sautoy's forehead as he said this. "I'm afraid", his webpage says, "I don't have time at present to look at unsolicted [sic] manuscripts." Would-be Ramanujans will have to seek another Hardy.



In one of the back rows, a twelve-year-old boy armed with a well-thumbed copy of Du Sautoy's 2007 book Finding Moonshine: A Mathematician's Journey Through Symmetry, was taking notes in a big, sloping hand. 'Human critical faculties', he had written.



Nakul Krishna teaches and researches Philosophy at the University of Oxford.

















































