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Numbers k such that gcd(2^k-69,k) > 1.
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%I #8 Feb 18 2022 08:12:07

%S 10,26,30,50,67,70,88,90,110,130,136,150,170,182,183,185,190,198,210,

%T 212,230,250,270,272,285,290,308,310,330,338,350,370,390,408,410,413,

%U 418,430,450,470,490,494,510,528,530,544,550,570,590,610,627,630,638,650

%N Numbers k such that gcd(2^k-69,k) > 1.

%C The corresponding gcd's are 5,13,5,5,67,5,11,5,5,5,17,5,5,13,61,37,5,11, ...

%H Amiram Eldar, <a href="/A125035/b125035.txt">Table of n, a(n) for n = 1..10000</a>

%e 10 is a term since gcd(2^10-69,10) = gcd(1024-69,10) = gcd(955,10) = 5 > 1.

%e Note that 67|(2^67-69).

%t Select[Range[650], ! CoprimeQ[2^# - 69, #] &] (* _Amiram Eldar_, Feb 18 2022 *)

%Y Cf. A124977, A125034.

%K nonn

%O 1,1

%A _Zak Seidov_, Nov 17 2006

%E More terms from _Amiram Eldar_, Feb 18 2022