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 A074478 #45 Jan 03 2024 23:53:53
%S A074478 2,3,13,7,313,521,601,449,11489,5167,9161,5281,390001,38923,234750601,
%T A074478 7621,29423041,41540861,6597973,213029,632133361,7603,1030330938209,
%U A074478 42272797713043,152587500001,50150933101,83181652304609,16018507
%N A074478 Largest prime factor of 5^n + 1.
%H A074478 <a href="/A074478/b074478.txt">Table of n, a(n) for n = 0..471</a>
%H A074478 S. S. Wagstaff, Jr., <a href="http://www.cerias.purdue.edu/homes/ssw/cun/index.html">The Cunningham Project</a>
%F A074478 a(n) = A006530(A034474(n)). - _Michel Marcus_, Jul 09 2016
%e A074478 5^11 + 1 = 48828126 = 2*3*23*67*5281, so a(11) = 5281.
%t A074478 Table[FactorInteger[5^n + 1][[-1, 1]], {n, 0, 30}] (* _Bruno Berselli_, Aug 23 2013 *)
%o A074478 (PARI) for(n=0,30, v=factor(5^n+1); print1(v[matsize(v)[1],1],","))
%o A074478 (Magma) [Maximum(PrimeDivisors(5^n+1)): n in [0..30]]; // _Vincenzo Librandi_, Jul 09 2016
%Y A074478 Cf. A002587 (largest prime factor of 2^n + 1), A074479 (largest prime factor of 5^n - 1), A074476 (largest prime factor of 3^n + 1), A227575 (largest prime factor of 7^n + 1).
%Y A074478 Cf. A006530, A034474.
%K A074478 nonn
%O A074478 0,1
%A A074478 _Rick L. Shepherd_, Aug 23 2002
%E A074478 Terms to a(100) in b-file from _Vincenzo Librandi_, Jul 09 2016
%E A074478 a(101)-a(451) in b-file from _Amiram Eldar_, Feb 01 2020
%E A074478 a(452)-a(471) in b-file from _Max Alekseyev_, Apr 25 2022, Jan 04 2024