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 A274907 #23 Apr 15 2025 22:25:32
%S A274907 5,7,43,37,311,43,55987,1297,2467,311,3154757,97,760891,55987,1201,
%T A274907 98801,30839,46441,638073026189,6781,1822428931,51828151,7505944891,
%U A274907 1678321,40185601,760891,623067280651,5030761,7369130657357778596659,1950271,49744740983476472807
%N A274907 Largest prime factor of 6^n - 1.
%H A274907 Max Alekseyev, <a href="/A274907/b274907.txt">Table of n, a(n) for n = 1..430</a> (terms 1..100 from Vincenzo Librandi, term 101..420 from Amiram Eldar)
%H A274907 J. Brillhart et al., <a href="http://dx.doi.org/10.1090/conm/022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%F A274907 a(n) = A006530(A024062(n)). - _Michel Marcus_, Jul 11 2016
%e A274907 6^5 - 1 = 7775 = 5*5*311, so a(5) = 311.
%t A274907 Table[FactorInteger[6^n - 1][[-1, 1]], {n, 40}]
%o A274907 (Magma) [Maximum(PrimeDivisors(6^n-1)): n in [1..40]];
%o A274907 (PARI) a(n) = vecmax(factor(6^n-1)[,1]); \\ _Michel Marcus_, Jul 13 2016
%Y A274907 Cf. A006530, A057955, A059888, A085031, A024062, A366620, A366621, A366622, A366623.
%Y A274907 Cf. similar sequences listed in A274906.
%K A274907 nonn
%O A274907 1,1
%A A274907 _Vincenzo Librandi_, Jul 11 2016