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A227575
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Largest prime factor of 7^n + 1.
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4
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2, 2, 5, 43, 1201, 191, 181, 911, 169553, 117307, 4021, 10746341, 1201, 228511817, 13564461457, 6568801, 47072139617, 29078814248401, 13841169553, 4058036683, 810221830361, 309079, 83960385389, 3421093417510114543, 33232924804801, 79787519018560501
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OFFSET
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0,1
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LINKS
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Amiram Eldar, Table of n, a(n) for n = 0..372 (terms 0..100 from Vincenzo Librandi)
S. S. Wagstaff, Jr., The Cunningham Project
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FORMULA
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a(n) = A006530(A034491(n)). - Vincenzo Librandi, Jul 12 2016
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EXAMPLE
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7^12 + 1 = 2*73*193*409*1201, so a(12) = 1201.
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MATHEMATICA
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Table[FactorInteger[7^n + 1][[-1, 1]], {n, 0, 30}] (* Bruno Berselli, Aug 23 2013 *)
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PROG
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(PARI) a(n) = f = factor(7^n + 1); f[#f~, 1]; \\ Michel Marcus, Aug 22 2013
(MAGMA) [Maximum(PrimeDivisors(7^n+1)): n in [0..30]]; // Bruno Berselli, Aug 23 2013
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CROSSREFS
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Cf. A006530, A034491.
Cf. A002587, A074249, A074476, A074478.
Sequence in context: A301346 A020549 A196128 * A114715 A270750 A234703
Adjacent sequences: A227572 A227573 A227574 * A227576 A227577 A227578
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KEYWORD
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nonn
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AUTHOR
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Michel Marcus, Aug 22 2013
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STATUS
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approved
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