[seqfan] Re: relation A033984 and A173138, solutions of mod n equations

[Maximilian Hasler]

I think the title of
A173138
Composite numbers n such that the congruence 2^(n-4)=1 (mod n) is solvable

is not well chosen ( ... solvable -> solution to ... ?!)

if n is odd, then 2^4 is invertible mod n so both equations are equivalent.

and there can't be a solution > 4 to the 2nd equation (...=1)  for
even n (which is explicitly excluded in A033984).

M.H.


On Sun, Feb 21, 2010 at 3:34 PM, Richard Mathar
<mathar at strw.leidenuniv.nl> wrote:
>
> How are these two sequences related?
>
> http://research.att.com/~njas/sequences/?q=id:A173138|id:A033984
>
> 4,40369,673663,990409,1697609,2073127,6462649,7527199,7559479,14421169,21484129,37825753,57233047,
>
> 40369,673663,990409,1697609,2073127,6462649,7527199,7559479,14421169,21484129,37825753,57233047,130647919,141735559,179203369,188967289,218206489,259195009,264538057,277628449,330662479,398321239,501126487,
>
>
>
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