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I am trying to find an expression that summarizes the following series:

...0.01  0.05  0.1  0.5  1  5 10 50 100 500...

I know this is a very simple question, but for some reason I can't think of any simple formula that summarizes the series above.

I was thinking about 10^n, with -2 < n < 2, but this doesn't give the 0.05, 0.5, etc. in between.

Care to give me some tips please?

Thanks so much for all the help!

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up vote 3 down vote accepted

Use an if. The ratio alternates between 2 and 5. You can also play at trick like this: $7/2 + 3/2*(-1)^n$. Make sure you get the phase right.

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