A094412 Numbers k that divide Fibonacci(k+1) but do not divide Fibonacci(k) + 1.

323, 377, 2834, 3827, 6479, 11663, 18407, 19043, 20999, 23407, 25877, 27323, 34943, 35207, 39203, 44099, 47519, 50183, 51983, 53663, 60377, 65471, 78089, 79547, 81719, 82983, 84279, 84419, 86063, 90287, 94667, 104663, 109871, 121103, 121393

Offset: 1

Author

Eric Rowland, May 01 2004

Keywords

• nonn

Links

• Giovanni Resta, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000045, A069107, A094395, A094401, A094411.

Programs

Mathematica

Select[Range[50000], ! Mod[Fibonacci[ # ] + 1, # ] == 0 && Mod[Fibonacci[ # + 1], # ] == 0 &]
Select[Range[122000],Divisible[{Fibonacci[#+1],Fibonacci[#]+1},#]=={True,False}&] (* Harvey P. Dale, Apr 16 2019 *)

PARI

fibmod(n,m)=(Mod([0,1;1,1],m)^n*[0;1])[1,1]
is(n)=fibmod(n+1,n)==0 && fibmod(n,n)!=-1 \\ Charles R Greathouse IV, Nov 04 2016