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 A121170 #13 Aug 01 2024 16:48:21
%S A121170 5,11,61,41,3001,61,141961,2161,109441,3001,474541,2521,14736206161,
%T A121170 141961,230686501,3041,3415914041,109441,67735001,570601,8288823481,
%U A121170 474541,2441738887963981,20641,158414167964045700001,14736206161,1114769954367361,12317523121,349619996930737079890201
%N A121170 Largest prime divisor of Fibonacci(5n).
%C A121170 Except for a(1) = 5 all a(n) are congruent to 1 (mod 10) (final digit is 1). Final digit of most prime divisors of F(5n) is 1.
%H A121170 Amiram Eldar, <a href="/A121170/b121170.txt">Table of n, a(n) for n = 1..284</a>
%F A121170 a(n) = A060385(5*n).
%e A121170 a(2) = 11 because F(10)= 5 * 11.
%e A121170 a(4) = 41 because F(20)= 3 * 5 * 11 * 41.
%e A121170 a(10) = 3001 because F(50)= 5^2 * 11 * 101 * 151 * 3001.
%e A121170 a(25) = 158414167964045700001 because F(125)= 5^3 * 3001 * 158414167964045700001.
%t A121170 Table[Max[Flatten[FactorInteger[Fibonacci[5n]]]],{n,1,50}]
%Y A121170 Cf. A000045, A060385.
%K A121170 nonn
%O A121170 1,1
%A A121170 _Alexander Adamchuk_, Aug 14 2006
%E A121170 a(27)-a(29) from _Amiram Eldar_, Aug 01 2024