[seqfan] A006521 and n dividing 2^n+1, but not 2^(n-1)+1
r.rosenthal at web.de
Mon Feb 22 23:29:45 CET 2010
In http://www.research.att.com/~njas/sequences/A006521 they say:
For a proof, see 
I think this simply means the first of the references given, but
it would be a good idea to have the numbers ,  etc. in
front of the references, just in case someone happened to add another
I admit that this is nitpicking squared and so I go straight on to
what I'm really interested in:
according to A006521 there are many (1)
numbers n which divide 2^n+1.
In a discussion in de.rec.denksport I learned that
no n > 1 does exist such that (2)
n divides 2^(n-1)+1.
I couldn't find any sequence related to this fact. I would like to
see a proof for (2).
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