A079506 - OEIS

A079506

Numbers k with gcd(2^k-1, Fibonacci(k)) > 1 and not divisible by 2 or 11. Odd members of A074776 not divisible by 11.

%I #8 May 14 2022 11:31:23

%S 261,305,333,377,525,651,753,783,895,915,999,1131,1305,1475,1525,1575,

%T 1665,1827,1885,1953,2135,2235,2259,2265,2283,2319,2331,2349,2515,

%U 2601,2625,2639,2685,2743,2745,2867,2921,2975,2997,3255,3393,3549,3675,3765

%N Numbers k with gcd(2^k-1, Fibonacci(k)) > 1 and not divisible by 2 or 11. Odd members of A074776 not divisible by 11.

%H Amiram Eldar, <a href="/A079506/b079506.txt">Table of n, a(n) for n = 1..10000</a>

%e Example: gcd(2^261-1, Fibonacci(261)) = 2089 and 11 does not divide 261, so 261 is in the sequence.

%t Select[2*Range[2000]-1, !Divisible[#, 11] && !CoprimeQ[2^# - 1, Fibonacci[#]] &] (* _Amiram Eldar_, May 14 2022 *)

%o (PARI) for(k=1,5000,if(gcd(2^k-1,fibonacci(k))>1,if(k%2,if(k%11,print1(k",")))))

%Y Cf. A000045, A000225, A074776.

%K nonn

%O 1,1

%A _Ralf Stephan_, Jan 21 2003