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Nth term of alternating series with two positive terms at beginning

  1. Mar 12, 2013 #1
    (I hope this is the right subforum)
    I'm talking about the series 1, 1, -1, 1, -1, 1, -1... I thought about it for a long time but I have no idea. If that first term were gone it would just be (-1)^(n+1), but...it's there...
  2. jcsd
  3. Mar 12, 2013 #2


    Staff: Mentor

    Just write it as 1 + your alternating series.
  4. Mar 12, 2013 #3


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    Science Advisor

    What's wrong with a1 = 1, and an = (-1)n for n > 1?
  5. Mar 12, 2013 #4
    Yeah that works, I was just wondering if there was a better way to do it.
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