The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A005422 Largest prime factor of 10^n - 1. (Formerly M2889) 7
 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; text; internal format)
 OFFSET 1,1 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. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Ray Chandler, Table of n, a(n) for n = 1..322 (first 100 terms from T. D. Noe) K. Beschorner, Factorizations of Repunit Numbers of the form (10^n-1)/9 (111111...). [Retrieved July 30, 2015] 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 FORMULA For n > 1, a(n) = A003020(n). For 1 < n < 10, a(n) = A075024(n). - M. F. Hasler, Jul 30 2015 a(n) = A006530(A002283(n)). - Vincenzo Librandi, Jul 13 2016 MAPLE A005422 := proc(n)     10^n-1 ;     A006530(%) ; end proc: # R. J. Mathar, Dec 02 2016 MATHEMATICA Table[FactorInteger[10^n - 1][[-1, 1]], {n, 1, 40}] (* Vincenzo Librandi, Jul 13 2016 *) PROG (PARI) a(n)=vecmax(factor(10^n-1)[, 1]) \\ Simplified by M. F. Hasler, Jul 30 2015 (MAGMA) [Maximum(PrimeDivisors(10^n-1)): n in [1..45]]; // Vincenzo Librandi, Jul 13 2016 CROSSREFS Same as A003020 except for the additional a(1) = 3. Cf. A002283, A006530, A067063, A075024, A102380. Cf. similar sequences listed in A274906. Sequence in context: A046107 A243110 A061075 * A040017 A007615 A065540 Adjacent sequences:  A005419 A005420 A005421 * A005423 A005424 A005425 KEYWORD nonn AUTHOR EXTENSIONS Edited by M. F. Hasler, Jul 30 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 1 12:29 EDT 2020. Contains 334762 sequences. (Running on oeis4.)