cp's OEIS Frontend

A002592 Largest prime factor of 9^n + 1.

%I A002592 M3994 N1655 #46 Sep 08 2022 08:44:31
%S A002592 2,5,41,73,193,1181,6481,16493,21523361,530713,42521761,570461,769,
%T A002592 4795973261,647753,47763361,926510094425921,1743831169,282429005041,
%U A002592 25480398173,128653413121,109688713,56625998353,70601370627701
%N A002592 Largest prime factor of 9^n + 1.
%D A002592 J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.
%D A002592 M. Kraitchik, Recherches sur la Théorie des Nombres. Gauthiers-Villars, Paris, Vol. 1, 1924, Vol. 2, 1929, see Vol. 2, p. 89.
%D A002592 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002592 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002592 <a href="/A002592/b002592.txt">Table of n, a(n) for n = 0..345</a>
%H A002592 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.
%H A002592 S. S. Wagstaff, Jr., <a href="http://www.cerias.purdue.edu/homes/ssw/cun/index.html">The Cunningham Project</a>
%F A002592 a(n) = A006530(A062396(n)). - _Vincenzo Librandi_, Jul 12 2016
%F A002592 a(n) = A074476(2*n). - _Max Alekseyev_, Apr 25 2022
%p A002592 for n from 0 to 30 do t1:=ifactor(9^n+1); od;
%t A002592 Table[FactorInteger[9^n + 1][[-1, 1]], {n, 0, 10}] (* _Vincenzo Librandi_, Jul 12 2016 *)
%o A002592 (Magma) [Maximum(PrimeDivisors(9^n+1)): n in [0..40]]; // _Vincenzo Librandi_, Jul 12 2016
%Y A002592 Cf. A006530, A062396, A274909.
%Y A002592 Cf. similar sequences listed in A274903.
%K A002592 nonn
%O A002592 0,1
%A A002592 _N. J. A. Sloane_
%E A002592 Terms up to a(315) in b-file from _Sean A. Irvine_, Apr 20 2014
%E A002592 Terms a(316)-a(345) in b-file from _Max Alekseyev_, Apr 24 2019, Sep 10 2020, Aug 26 2021, Apr 25 2022