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A074249
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a(n) = largest prime factor of 7^n-1.
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12
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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
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OFFSET
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1,1
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LINKS
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FORMULA
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MATHEMATICA
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Join[{1}, Table[FactorInteger[7^n - 1] [[-1, 1]], {n, 30}]] (* Vincenzo Librandi, Aug 23 2012 *)
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PROG
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(PARI) a(n) = vecmax(factor(7^n-1)[, 1]); \\ Michel Marcus, Dec 16 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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a(0) removed and a(379)-a(388) in b-file added by Max Alekseyev, Apr 25 2022, Sep 11 2022
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STATUS
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approved
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