4.12.03

NEW MERSENNE PRIME. There's something appealing about searching for prime numbers by taking powers of 2 and subtracting 1, 2**n - 1. There's also something appealing about searching by taking prime powers of 2, although you quickly see that prime-ness does not follow, e.g. 2**2 - 1 = 3, a prime; 2**3 - 1 = 7, a prime, 2**5 - 1 = 31, a prime, 2**7 - 1 = 127, a prime, 2**11 - 1 = 2047 = 23*89, a product of two primes, and then they start to thin out. Marginal Revolution reports the discovery of the 40th such Mersenne prime, with power 20,996,011, and links to a spare computing power sharing opportunity, for people with computer time to spare and an interest in chasing primes. (There are still as many to find today as there were yesterday.)

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