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A006990
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Largest prime <= n!.
(Formerly M1541)
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11
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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; refs; listen; history; internal format)
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OFFSET
| 2,1
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COMMENTS
| 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
| N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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MATHEMATICA
| PrevPrime[ n_Integer ] := Module[ {k = n - 1}, While[ ! PrimeQ[ k ], k-- ]; k ]; Table[ PrevPrime[ n! ], {n, 3, 25} ]
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CROSSREFS
| Sequence in context: A100299 A038833 A003501 * A032182 A165902 A191600
Adjacent sequences: A006987 A006988 A006989 * A006991 A006992 A006993
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com)
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EXTENSIONS
| More terms from Jud McCranie (JudMcCranie(AT)ugaalum.uga.edu); also from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 03 2001
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