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A023173 Numbers k such that Fibonacci(k) == 1 (mod k). 12

%I #27 Apr 11 2022 12:15:13

%S 1,2,11,19,22,29,31,38,41,58,59,61,62,71,79,82,89,101,109,118,122,131,

%T 139,142,149,151,158,178,179,181,191,199,202,211,218,229,239,241,251,

%U 262,269,271,278,281,298,302,311,323,331,349,358,359,362,379,382,389,398,401

%N Numbers k such that Fibonacci(k) == 1 (mod k).

%C Sequence contains 1, A064739(k) for all k>=0, 2*A064739(k) for k>1. - _Benoit Cloitre_, Apr 06 2002

%H Charles R Greathouse IV, <a href="/A023173/b023173.txt">Table of n, a(n) for n = 1..10000</a>

%t lst={};Do[If[Mod[Fibonacci[n],n]==1,AppendTo[lst,n]],{n,1,7!}];Take[Union[lst],5! ] (* _Vladimir Joseph Stephan Orlovsky_, Apr 03 2009 *)

%t Select[Range[500],Mod[Fibonacci[#]-1,#]==0&] (* _Harvey P. Dale_, Sep 22 2021 *)

%o (PARI) fibmod(n,m)=((Mod([1,1;1,0],m))^n)[1,2]

%o is(n)=fibmod(n,n)==1 \\ _Charles R Greathouse IV_, Oct 06 2016

%Y Cf. A000045, A045468, A003631, A064739.

%K nonn,easy

%O 1,2

%A _David W. Wilson_

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Last modified April 24 15:57 EDT 2024. Contains 371961 sequences. (Running on oeis4.)