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Numbers k that divide 2^k + 5.
6

%I #28 Aug 16 2021 03:23:54

%S 1,7,133,1517,11761,676333,1484413,3627557,10289371,1449045241,

%T 2433687407,12309023183,29013950411,11701492535299,223598572318157,

%U 362232879754103

%N Numbers k that divide 2^k + 5.

%C No other terms below 10^15. Some large terms: 37367159696063084325121, 1637537600494693555095121, 50692913747901869910332539, 407*(2^407+5)/1125038874668278099 (108 digits). - _Max Alekseyev_, Sep 22 2016

%H OEIS Wiki, <a href="/wiki/2^n mod n">2^n mod n</a>

%e 2^7 + 5 = 133 is divisible by 7. Thus 7 is a term of this sequence.

%t Select[Range[10^5], Divisible[2^# + 5, #] &] (* _Robert Price_, Oct 12 2018 *)

%o (PARI)

%o for(n=1,10^9,if(Mod(2,n)^n==Mod(-5,n),print1(n,", ")))

%Y Cf. A128121, A168614.

%K nonn,more

%O 1,2

%A _Derek Orr_, Jul 17 2014

%E a(10)-a(13) from _Lars Blomberg_, Nov 05 2014

%E a(14)-a(16) from _Max Alekseyev_, Oct 09 2016