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A002585
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Largest prime factor of 1 + (product of first n primes).
(Formerly M2697 N1081)
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11
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3, 7, 31, 211, 2311, 509, 277, 27953, 703763, 34231, 200560490131, 676421, 11072701, 78339888213593, 13808181181, 18564761860301, 19026377261, 525956867082542470777, 143581524529603, 2892214489673, 16156160491570418147806951, 96888414202798247, 1004988035964897329167431269
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OFFSET
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1,1
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COMMENTS
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Based on Euclid's proof that there are infinitely many primes.
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REFERENCES
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M. Kraitchik, On the divisibility of factorials, Scripta Math., 14 (1948), 24-26 (but beware errors).
M. Kraitchik, Introduction à la Théorie des Nombres. Gauthier-Villars, Paris, 1952, p. 2.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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S. Kravitz and D. E. Penney, An extension of Trigg's table, Math. Mag., 48 (1975), 92-96. [Annotated scanned copy; also letter from N. J. A. Sloane to John Selfridge]
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FORMULA
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MATHEMATICA
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FactorInteger[#][[-1, 1]]&/@Rest[FoldList[Times, 1, Prime[Range[30]]]+1] (* Harvey P. Dale, Apr 10 2012 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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EXTENSIONS
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Terms a(82)-a(87) in b-file added by Amiram Eldar, Feb 13 2020
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STATUS
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approved
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