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 A105800 #18 Feb 16 2025 08:32:57
%S A105800 1,1,1,1,1,2,1,3,2,5,1,8,1,13,5,21,1,34,1,55,13,89,1,144,5,233,34,377,
%T A105800 1,610,1,987,89,1597,13,2584,1,4181,233,6765,1,10946,1,17711,610,
%U A105800 28657,1,46368,13,75025,1597,121393,1,196418,89,317811,4181,514229,1,832040,1
%N A105800 Greatest Fibonacci number that is a proper divisor of the n-th Fibonacci number; a(1) = a(2) = 1.
%C A105800 a(A001605(n)) = 1.
%H A105800 Antti Karttunen, <a href="/A105800/b105800.txt">Table of n, a(n) for n = 1..987</a>
%H A105800 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FibonacciNumber.html">Fibonacci Number</a>
%H A105800 Wikipedia, <a href="https://en.wikipedia.org/wiki/Divisibility_sequence">Divisibility sequence</a>
%F A105800 From _Antti Karttunen_, Jan 11 2017: (Start)
%F A105800 a(n) = A280686(A000045(n)).
%F A105800 a(n) = A000045(A032742(n)). [Because A000045 is a divisibility sequence.]
%F A105800 a(A032742(n)) = A280688(n).
%F A105800 (End)
%t A105800 nn=70;Join[{1,1},With[{fibs=Fibonacci[Range[nn]]},Table[ Max[ Intersection[ Most[Divisors[fibs[[n]]]],fibs]],{n,3,nn}]]] (* _Harvey P. Dale_, Apr 10 2012 *)
%Y A105800 Cf. A000045, A032742, A076984, A139045, A280686, A280688, A280689, A280690, A280698, A280699.
%Y A105800 Cf. A046022 (gives the positions of ones).
%K A105800 nonn
%O A105800 1,6
%A A105800 _Reinhard Zumkeller_, Apr 20 2005