Question 622974: conjecture a formula for the sequence.
3, 5, 11, 21, 43, 85, 171, 341, 683, 1365
Answer by math-vortex(648)   (Show Source):
You can put this solution on YOUR website! Hi, there--
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These look like Jacobsthal numbers, except that that sequence starts with 0, 1, 1, 3, 5, 11, ...
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This sequence is similar to the Fibonacci sequence. Each number is the sequence is found by adding the number preceding it to twice the number before that.
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For example, in your sequence
11 is 5 plus two times 3.
21 is 11 plus two times 5.
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Here's a wikipedia link: http://en.wikipedia.org/wiki/Jacobsthal_number
You can also google Jacobsthal numbers and find all sorts of cool stuff. Hope this helps.
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Ms.Figgy
math.in.the.vortex@gmail.com
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