This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A094401 #17 Feb 16 2025 08:32:53
%S A094401 2737,4181,6721,13201,15251,34561,51841,64079,64681,67861,68251,90061,
%T A094401 96049,97921,118441,146611,163081,179697,186961,194833,197209,219781,
%U A094401 252601,254321,257761,268801,272611,283361,302101,303101,327313,330929
%N A094401 Composite n such that n divides both Fibonacci(n-1) and Fibonacci(n) - 1.
%C A094401 Composite n such that Q^(n-1) = I (mod n), where Q is the Fibonacci matrix {{1,1},{1,0}} and I is the identity matrix. The identity is also true for the primes congruent to 1 or 4 (mod 5), which is sequence A045468. The period of Q^k (mod n) is the same as the period of the Fibonacci numbers F(k) (mod n), A001175. Hence the terms in this sequence are the composite n such that A001175(n) divides n-1. [_T. D. Noe_, Jan 09 2009]
%H A094401 Giovanni Resta, <a href="/A094401/b094401.txt">Table of n, a(n) for n = 1..1000</a> (first 200 terms from T. D. Noe)
%H A094401 Eric Weisstein, <a href="https://mathworld.wolfram.com/FibonacciQ-Matrix.html">MathWorld: Fibonacci Q-Matrix</a>.
%t A094401 Select[Range[2, 50000], ! PrimeQ[ # ] && Mod[Fibonacci[ # - 1], # ] == 0 && Mod[Lucas[ # ] - 1, # ] == 0 &]
%Y A094401 Cf. A005845, A069106, A094394, A094400.
%K A094401 nonn
%O A094401 1,1
%A A094401 _Eric Rowland_, May 01 2004
%E A094401 More terms from _Ryan Propper_, Sep 24 2005