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 A003021 Largest prime factor of 10^n + 1. (Formerly M2007) 10
 2, 11, 101, 13, 137, 9091, 9901, 909091, 5882353, 52579, 27961, 8779, 99990001, 1058313049, 121499449, 9091, 69857, 21993833369, 999999000001, 909090909090909091, 5964848081, 909091, 1056689261, 549797184491917 (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. Ehrhard Behrends, Five-Minute Mathematics, translated by David Kramer. American Mathematical Society (2008) p. 7 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002. T. Granlund, Factors of 10^n + 1 Makoto Kamada, Factorizations of 100...001. S. S. Wagstaff, Jr., The Cunningham Project FORMULA a(n) = A006530(A062397(n)). - Vincenzo Librandi, Jul 12 2016 MATHEMATICA Table[FactorInteger[10^n + 1][[-1, 1]], {n, 0, 29}] (* Alonso del Arte, Oct 21 2011 *) PROG (PARI) for(n=0, 1e2, p=factor(10^n+1)[omega(10^n+1), 1]; print1(p, ", ")) \\ Felix FrÃ¶hlich, Aug 13 2014 (MAGMA) [Maximum(PrimeDivisors(10^n+1)): n in [0..40]]; // Vincenzo Librandi, Jul 12 2016 CROSSREFS Cf. A006530, A062397. Sequence in context: A001271 A038371 A236174 * A097463 A263607 A083394 Adjacent sequences:  A003018 A003019 A003020 * A003022 A003023 A003024 KEYWORD nonn,easy,changed AUTHOR EXTENSIONS More terms from Jason Earls, Jul 11 2001 Terms up to a(280) in b-file from D. S. McNeil, Oct 22 2011 a(281)-a(310) in b-file from Ray Chandler, May 02 2017 a(311)-a(331) in b-file from Max Alekseyev, Apr 24 2019, Feb 13 2020, May 13 2022 STATUS approved

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Last modified May 18 23:31 EDT 2022. Contains 353826 sequences. (Running on oeis4.)