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Search: id:A006990
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| A006990 |
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Largest prime <= n!.
(Formerly M1541)
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+0
10
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| 2, 5, 23, 113, 719, 5039, 40289, 362867, 3628789, 39916787, 479001599, 6227020777, 87178291199, 1307674367953, 20922789887947, 355687428095941, 6402373705727959, 121645100408831899, 2432902008176639969
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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Conjecture: for n > 2, n! - a(n) is 1 or a prime i.e. a non-composite number. E.g. 3! - 5 = 1, 5!- 113 = 7 etc. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 19 2002
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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MATHEMATICA
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PrevPrime[ n_Integer ] := Module[ {k = n - 1}, While[ ! PrimeQ[ k ], k-- ]; k ]; Table[ PrevPrime[ n! ], {n, 3, 25} ]
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CROSSREFS
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Sequence in context: A100299 A038833 A003501 this_sequence A032182 A165902 A167142
Adjacent sequences: A006987 A006988 A006989 this_sequence A006991 A006992 A006993
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com)
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EXTENSIONS
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More terms from Jud McCranie (j.mccranie(AT)comcast.net); also from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 03 2001
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