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A005422
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Largest prime factor of 10^n -1.
(Formerly M2889)
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6
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3, 11, 37, 101, 271, 37, 4649, 137, 333667, 9091, 513239, 9901, 265371653, 909091, 2906161, 5882353, 5363222357, 333667, 1111111111111111111, 27961, 10838689, 513239, 11111111111111111111111, 99990001, 182521213001, 1058313049
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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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.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..100 (derived from Yousuke Koide)
J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
Yousuke Koide, Factorizations of Repunit Numbers
S. S. Wagstaff, Jr., The Cunningham Project
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PROG
| (PARI) a(n)=local(p); if(n<1, 0, p=factor(10^n-1)~[1, ]; p[length(p)])
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CROSSREFS
| Same as A003020 except for initial terms. Cf. A102380, A067063.
Sequence in context: A007138 A046107 A061075 * A040017 A007615 A065540
Adjacent sequences: A005419 A005420 A005421 * A005423 A005424 A005425
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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