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A139467
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Largest prime factor of n! + 2n - 1.
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3
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2, 5, 11, 31, 43, 43, 163, 2689, 362897, 3628819, 179, 1908373, 800903, 101341, 13999747, 104099179, 10778406912001, 1300448327, 356961701, 62382102773760001, 10367823077693, 11437176299, 102338720137
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..23.
Florian Luca and Igor E. Shparlinski, On the largest prime factor of n! + 2^n - 1, Journal de Theorie des Nombres de Bordeaux 17 (2005), 859-870.
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MATHEMATICA
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a = {}; Do[k = n! + 2 n - 1; c = First[Last[FactorInteger[k]]]; AppendTo[a, c], {n, 1, 40}]; a (*Artur Jasinski*)
Table[FactorInteger[n!+2n-1][[-1, 1]], {n, 30}] (* From Harvey P. Dale, Aug 31 2011 *)
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PROG
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(PARI) a(n)=my(f=factor(n!+2*n-1)[, 1]); f[#f] \\ Charles R Greathouse IV, Feb 01 2013
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CROSSREFS
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Cf. A127986, A127987, A139023, A139024, A139464, A139465, A139466.
Sequence in context: A131347 A079225 A139466 * A124481 A002862 A190865
Adjacent sequences: A139464 A139465 A139466 * A139468 A139469 A139470
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski, Apr 22 2008
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STATUS
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approved
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