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A101016
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Indices of primes in sequence defined by A(0) = 91, A(n) = 10*A(n-1) + 71 for n > 0.
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0
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5, 8, 89, 110, 209, 236, 413, 1191, 1259, 5835, 6771
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OFFSET
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1,1
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COMMENTS
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Numbers n such that (890*10^n - 71)/9 is prime.
Numbers n such that digit 9 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.
Numbers corresponding to terms <= 413 are certified primes.
Certified primality of terms corresponding to 1191 and 1259 with Primo. - Ryan Propper (rpropper(AT)stanford.edu), Jun 20 2005
Next term after 6771 is greater than 10000. - Ryan Propper (rpropper(AT)stanford.edu), Jun 20 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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Table of n, a(n) for n=1..11.
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EXAMPLE
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9888881 is prime, hence 5 is a term.
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PROG
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(PARI) a=91; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+71)
(PARI) for(n=0, 1500, if(isprime((890*10^n-71)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103107(n) - 1.
Sequence in context: A213239 A123819 A153720 * A025518 A151827 A162571
Adjacent sequences: A101013 A101014 A101015 * A101017 A101018 A101019
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KEYWORD
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nonn,hard,more
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AUTHOR
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Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004
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EXTENSIONS
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Two additional terms, corresponding to probable primes, from Ryan Propper (rpropper(AT)stanford.edu), Jun 20 2005
Edited by T. D. Noe, Oct 30 2008
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STATUS
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approved
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