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Old 2021-05-08, 15:52   #6
a1call
 
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"Rashid Naimi"
Oct 2015
Remote to Here/There

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Nice.
A numeric example for 2n-1 = 65:

https://www.wolframalpha.com/input/?...er+the+integer

ETA:
No solutions for 2n-1 = 21 even though it is of the form 4m+1 since it has at least one prime factor of the form 2m+1 with odd m:

https://www.wolframalpha.com/input/?...er+the+integer

Last fiddled with by a1call on 2021-05-08 at 16:44
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