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Search: id:A056266
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| A056266 |
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Indices of primes in sequence defined by A(0) = 99, A(n) = 10*A(n-1) - 1 for n > 0. |
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+0
2
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OFFSET
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1,1
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COMMENT
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Numbers n such that (890*10^n + 1)/9 is prime.
Numbers n such that the number 9 8(n times) 9 is prime.
Numbers corresponding to terms <= 983 are certified primes. For number corresponding to 1225 see P. De Geest, PDP Reference Table.
a(n) = A082719(n-1) - 2.
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REFERENCES
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Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, in preparation.
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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LINKS
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P. De Geest, PDP Reference Table
Makoto Kamada, Factorizations of 988...889.
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EXAMPLE
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9888889 is prime, hence 5 is a term.
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PROGRAM
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(PARI) a=99; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-1)
(PARI) for(n=0, 1500, if(isprime((890*10^n+1)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275, A082719.
Sequence in context: A135438 A015502 A101019 this_sequence A157860 A125242 A102976
Adjacent sequences: A056263 A056264 A056265 this_sequence A056267 A056268 A056269
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KEYWORD
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nonn,hard,more
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 18 2000
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EXTENSIONS
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Additional comments from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004
Edited by N. J. A. Sloane (njas(AT)research.att.com), Apr 17 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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