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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 October 23 23:51 EDT 2019. Contains 328379 sequences. (Running on oeis4.)