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Rule for a Sequence

Date: 8/25/96 at 14:4:55
From: Anonymous
Subject: Rule for a Sequence

I need to find out the next number in these two sequences:

   8 13 5 15 20 12    
  20 25 17 51 56 48 

They both follow the same rule, but I've had trouble finding it. 
Could you please help?


Date: 8/25/96 at 14:57:28
From: Doctor Robert
Subject: Re: Rule for a Sequence

It seems to me that the following algorithm gives you the correct 
terms in your sequence, starting with the first term in each:

  add five
  subtract eight
  multiply by three

You keep on repeating these three steps.  Am I correct?

The next term in the top sequence would be 36.
The next term in the lower sequence would be 144.

-Doctor Robert,  The Math Forum
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Associated Topics:
High School Sequences, Series

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