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MARY HENRY, whose abstract art is a particular delight for lovers of geometry, has died aged 96. An exhibition of her work can be seen at PDX Contemporary Art, 925 NW Flanders, Portland, OR 97209 until the end of May. New biggest prime foundThe biggest prime number yet has been found with some 12,978,189 digits. It would fill nearly 20 paperbacks if printed out. It's also the 45^{th} known Mersenne prime, a rare sort of prime written as a power of 2 subtract 1: 2^{43,112,609} − 1. That's 2 multiplied by itself 43,112,609 times and then subtract 1. A prime number can only be divided by the number 1 and itself — it has only two factors. The discovery by the UCLA math department qualified for a $100,000 award for the first prime of more than 10 million digits. It was discovered using software from the Greater Internet Mersenne Prime Search — GIMPS — that allows anyone with a PC or laptop to help search for the next largest prime. This new big prime was discovered in August 2008. Just two weeks later another — smaller — 46^{th} Mersenne prime was discovered near Cologne, Germany: 2^{ 37,156,667} − 1. It has a mere 11,185,272 digits. Mersenne primes were first discovered by the French monk and mathematician Marin Mersenne more than 300 years ago. Searching for primes was the sort of thing maths people did for fun, they still do. But now superbig primes are vital in internet and banking security as well as writing ultrasecret codes. Mathematicians know there are an infinite number of primes. They think there an infinite number of Mersenne primes, but the conjecture has yet to be proved. 

