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Showing posts with the label group theory

142857

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Here's a puzzle: Multiply 142857 by 2 and you get 285714 which has the same digits Multiply 142857 by 3 and you get 428571 which has the same digits Multiply 142857 by 4 and you get 571428 which has the same digits  In fact you keep getting permutations of 142857  till you get to a multiple of 7 at which point you get 999999.   Why? I can't remember now how I figured it out, but I do remember not being able to sleep, then having some sort of eureka moment and running downstairs in the middle of the night to scribble down the answer. The solution involves some group theory, which I studied last century when I did my Maths degree at Bristol.  Periodically I have a little panic that I've forgotten everything I learned there, and I refresh my memory.  I think it must have been after one of these episodes that my subconscious linked it to this strange number that I probably first came across at school.  Anyway, the s...