

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, FiveMinute 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.


FORMULA



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 Fröhlich, Aug 13 2014
(Magma) [Maximum(PrimeDivisors(10^n+1)): n in [0..40]]; // Vincenzo Librandi, Jul 12 2016


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



EXTENSIONS

a(311)a(331) in bfile from Max Alekseyev, Apr 24 2019, Feb 13 2020, May 13 2022


STATUS

approved



