Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #12 Aug 29 2020 06:57:25
%S 1,2,3,5,6,7,9,13,14,15,17,19,21,23,25,26,27,29,31,34,35,37,38,39,41,
%T 42,43,45,46,47,49,51,53,57,59,61,62,63,65,67,69,71,73,74,75,79,81,82,
%U 83,85,86,87,89,91,93,94,95,97,98,101,102,103,105,106,107,109,111,113
%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="/A074780/b074780.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) seems to be asymptotic to c*n with c=1.7...
%t Select[Range[120],CoprimeQ[2^#-1,Fibonacci[#]]&] (* _Harvey P. Dale_, Nov 27 2015 *)
%Y Complement of A074776.
%Y Cf. A000045, A000225.
%K nonn
%O 1,2
%A _Benoit Cloitre_, Sep 07 2002