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Search: id:A101153
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| A101153 |
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Indices of primes in sequence defined by A(0) = 79, A(n) = 10*A(n-1) - 1 for n > 0. |
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1
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OFFSET
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1,2
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COMMENT
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Numbers n such that (710*10^n + 1)/9 is a prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 8 followed by digit 9 is a prime.
Numbers corresponding to terms <= 54 are certified primes.
The next term after 1883 is greater than 5000. - Ryan Propper (rpropper(AT)stanford.edu), Jun 16 2005
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REFERENCES
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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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Makoto Kamada, Factorizations of 788...889.
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EXAMPLE
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78889 is a prime, hence 3 is a term.
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PROGRAM
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(PARI) a=79; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-1)
(PARI) for(n=0, 1000, if(isprime((710*10^n+1)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103067(n) - 1.
Sequence in context: A082372 A128107 A060860 this_sequence A045436 A007348 A105882
Adjacent sequences: A101150 A101151 A101152 this_sequence A101154 A101155 A101156
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KEYWORD
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nonn,hard,more
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 03 2004
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EXTENSIONS
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3 more terms from Ryan Propper (rpropper(AT)stanford.edu), Jun 16 2005
6840 from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007
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