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 Even, or Odd? (Posted on 2005-06-20)
1, 2, 2, 1, 2, 2, 4, 2, 8, 4, 32, 8, 256, ?, ?, ?, ...

 See The Solution Submitted by Dustin Rating: 2.0000 (1 votes)

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 I think you all are overthinking this... (spoiler) | Comment 12 of 14 |

I agree with Lisa's answers--I got the same numbers but arrived at them in a different way:

Taking only the odd numbered positions in the sequence:

1, , 2, , 2, , 4, , 8, , 32, , 256, , ...

You see that after the first two positions, the next position is the product of the previous two: 8192, 2097152, 17179869184, ...

Taking only the even numbered positions in the sequence:

, 2, , 1, , 2, , 2, , 4, , 8, , ...

You see that after the first two positions, the next position is the product of the previous two (just like with the odd numbered positions): 32, 256, 8192, ...

No logs or fancy alternating +/- is required if you recognise that this sequence consists of two interleaved sequences.

 Posted by Erik O. on 2005-06-21 15:28:13

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