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%I #12 May 08 2022 08:47:33
%S 1,2,3,4,5,6,7,8,9,11,12,13,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
%T 29,31,32,33,34,35,37,38,39,40,41,43,44,45,46,47,48,49,51,52,53,55,56,
%U 57,58,59,60,61,62,63,64,65,66,67,68,69,71,72,73,75,76,77,78,79,80,81
%N Numbers k such that 2^k+1 and F(k) are relatively prime, where F(k) denotes the k-th Fibonacci number.
%H Amiram Eldar, <a href="/A074779/b074779.txt">Table of n, a(n) for n = 1..10000</a>
%H Amiram Eldar, <a href="/A074779/a074779.jpg">Plot of a(n)/n for n = 1..10000</a>
%F a(n) seems to be asymptotic to c*n with c = 1.207...
%t Select[Range[100], CoprimeQ[2^# + 1, Fibonacci[#]] &] (* _Amiram Eldar_, May 08 2022 *)
%Y Cf. A000045, A000051.
%K nonn
%O 1,2
%A _Benoit Cloitre_, Sep 07 2002