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Every other odd number representation

  1. Jul 27, 2014 #1

    Maylis

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    Hello,

    Is there any formula that describes every other odd number, for ##n = 1,2,\dots##? I can't seem to find anything that does it on the web.

    Something that would do 1,5,9,13,...
     
  2. jcsd
  3. Jul 27, 2014 #2
    Try 2n - 1
    2n guarantees even
    Subtract 1 produces an odd number.
     
  4. Jul 27, 2014 #3

    Maylis

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    yeah but I said every other odd, not every odd
     
  5. Jul 27, 2014 #4
    4n-3? Or am I missing something really obvious?
     
  6. Jul 27, 2014 #5

    AlephZero

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    If "2n + something" gives a series of numbers separated by 2, what do you think gives a series separated by 4?

    EDIT: Oh well, I was trying to get you to think it out for yourself, but somebody else just told you the answer.
     
  7. Jul 27, 2014 #6

    HallsofIvy

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    Then 4n- 3 of course. (4n- 1 gives the other odd numbers, 3, 7, 11, etc.)
     
  8. Jul 27, 2014 #7

    HallsofIvy

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    Note that the last three of us, essentially saying the same thing, posted within 2 minutes!
     
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