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A002592 Largest prime factor of 9^n + 1.
(Formerly M3994 N1655)
4
2, 5, 41, 73, 193, 1181, 6481, 16493, 21523361, 530713, 42521761, 570461, 769, 4795973261, 647753, 47763361, 926510094425921, 1743831169, 282429005041, 25480398173, 128653413121, 109688713, 56625998353, 70601370627701 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.

M. Kraitchik, Recherches sur la Théorie des Nombres. Gauthiers-Villars, Paris, Vol. 1, 1924, Vol. 2, 1929, see Vol. 2, p. 89.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n = 0..330

J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.

S. S. Wagstaff, Jr., The Cunningham Project

FORMULA

a(n) = A006530(A062396(n)). - Vincenzo Librandi, Jul 12 2016

MAPLE

for n from 0 to 30 do t1:=ifactor(9^n+1); od;

MATHEMATICA

Table[FactorInteger[9^n + 1][[-1, 1]], {n, 0, 10}] (* Vincenzo Librandi, Jul 12 2016 *)

PROG

(MAGMA) [Maximum(PrimeDivisors(9^n+1)): n in [0..40]]; // Vincenzo Librandi, Jul 12 2016

CROSSREFS

Cf. A006530, A062396.

Cf. similar sequences listed in A274903.

Sequence in context: A106885 A072439 A286560 * A054553 A185052 A088547

Adjacent sequences:  A002589 A002590 A002591 * A002593 A002594 A002595

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

Terms up to a(315) in b-file from Sean A. Irvine, Apr 20 2014

Terms a(316)-a(330) in b-file from Max Alekseyev, Apr 24 2019

STATUS

approved

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Last modified June 6 14:04 EDT 2020. Contains 334827 sequences. (Running on oeis4.)