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 A074249 a(0) = 1; for n > 0, a(n) = largest prime factor of 7^n-1. 4
 1, 3, 3, 19, 5, 2801, 43, 4733, 1201, 1063, 2801, 293459, 181, 16148168401, 4733, 159871, 169553, 2767631689, 117307, 4534166740403, 4021, 11898664849, 10746341, 31479823396757, 1201, 31280679788951, 16148168401, 2583253 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..80 FORMULA a(n) = A006530(A024075(n)) for n >= 1. - Michel Marcus, Dec 16 2017 MATHEMATICA Join[{1}, Table[FactorInteger[7^n - 1] [[-1, 1]], {n, 30}]] (* Vincenzo Librandi, Aug 23 2012 *) PROG (PARI) a(n) = if (n==0, 1, vecmax(factor(7^n-1)[, 1])); \\ Michel Marcus, Dec 16 2017 CROSSREFS Cf. A006530, A024075. Sequence in context: A096935 A136475 A143180 * A234018 A101617 A131443 Adjacent sequences:  A074246 A074247 A074248 * A074250 A074251 A074252 KEYWORD nonn AUTHOR N. J. A. Sloane, Sep 26 2002 EXTENSIONS More terms from Benoit Cloitre, Sep 29 2002 STATUS approved

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Last modified March 26 06:58 EDT 2019. Contains 321481 sequences. (Running on oeis4.)