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Old 2008-04-23, 17:45   #1
davar55
 
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May 2004
New York City

423210 Posts
Default Sequence Question

(In the spirit of the 3N+1 sequence question...)

Start with any positive integer N.

If N is prime (or 1) replace it with 2N+1.
If N is composite, replace it with its largest prime factor.
Repeat these steps.

For example, if N=3 we get the cycle
3 -> 7 -> 15 -> 5 -> 11 -> 23 -> 47 -> 95 -> 19 -> 39 -> 13 -> 27 -> 3.

The question is: does every N eventually evolve into this cycle?
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