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A005381
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Numbers n such that n and n-1 are composite.
(Formerly M4598)
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6
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9, 10, 15, 16, 21, 22, 25, 26, 27, 28, 33, 34, 35, 36, 39, 40, 45, 46, 49, 50, 51, 52, 55, 56, 57, 58, 63, 64, 65, 66, 69, 70, 75, 76, 77, 78, 81, 82, 85, 86, 87, 88, 91, 92, 93, 94, 95
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Position where the composites first outnumber the primes by n, among the first natural numbers. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 11 2006
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REFERENCES
| M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 844.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
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CROSSREFS
| Equals A068780 + 1. Cf. A007921.
Sequence in context: A020199 A114844 A194593 * A175090 A197113 A099616
Adjacent sequences: A005378 A005379 A005380 * A005382 A005383 A005384
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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