# SOLUTION: conjecture a formula for the sequence. 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365

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 Algebra: Sequences of numbers, series and how to sum them Solvers Lessons Answers archive Quiz In Depth

 Question 622974: conjecture a formula for the sequence. 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365Answer by math-vortex(472)   (Show Source): You can put this solution on YOUR website!Hi, there-- . These look like Jacobsthal numbers, except that that sequence starts with 0, 1, 1, 3, 5, 11, ... . 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. . For example, in your sequence 11 is 5 plus two times 3. 21 is 11 plus two times 5. . 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. . Ms.Figgy math.in.the.vortex@gmail.com