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A simple challenge in Le Monde this week: find the group of four primes such that any sum of three terms in the group is prime and the overall sum is minimised. Here is a quick exploration by simulation, using the schoolmath package (with its imperfections): A=primes(start=1,end=53)[... [Read more...]

Neil Gunther has pointed out on his blog that the prime number decomposition R package schoolmath contains mistakes in the function primes, listing 1 as a prime number but also including decomposable numbers like 133 in its list of prime numbers: __ primes(100,140) [1] 101 107 111 113 123 129 131 137 __ primes(50,140) [1]  [...] [Read more...]

Recently Microsoft Office Outlook 2007 started giving me the vague error message Outlook cannot open this item. The item may be damaged. The message would appear randomly throughout the day. Sometimes five error message boxes would be stacked up on top of each other. OK, but which item? What kind of ... [Read more...]