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A007647
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Numbers n such that n*10^n + 1 is prime.
(Formerly M2783)
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1
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OFFSET
| 1,2
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COMMENTS
| These are generalized Cullen numbers in base 10. - Julien Peter Benney (jpbenney(AT)ftml.net), Oct 24 2004
No others less than 174000. - Julien Peter Benney (jpbenney(AT)ftml.net), Jun 11 2005
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REFERENCES
| J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 363, p. 84, Ellipses, Paris 2008.
H. Dubner, Generalized Cullen numbers, J. Rec. Math., 21 (No. 3, 1989), 190-191.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Daniel Hermle, First Coordinated Generalized Cullen Prime Search
Guenter Loeh, Generalized Cullen primes.
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EXAMPLE
| For n = 3 we get (3*10^3)+1 = (3*1000)+1 = 3000 + 1 = 3001, which is prime.
For n = 9 we get 9*10^9+1 = 9*1000000000+1 = 9000000000+1 = 9000000001, which is prime.
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CROSSREFS
| Cf. A004023.
Sequence in context: A193374 A191998 * A098980 A063586 A131477 A002128
Adjacent sequences: A007644 A007645 A007646 * A007648 A007649 A007650
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KEYWORD
| hard,nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Julien Peter Benney (jpbenney(AT)ftml.net), Jun 11 2005
Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion of Andrew Plewe, Jun 05 2007
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