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Search: id:A101540
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| A101540 |
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Indices of primes in sequence defined by A(0) = 69, A(n) = 10*A(n-1) - 1 for n > 0. |
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1
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OFFSET
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1,1
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COMMENT
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Numbers n such that (620*10^n + 1)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 8 followed by digit 9 is prime.
Numbers corresponding to terms <= 724 are certified primes.
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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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EXAMPLE
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688889 is prime, hence 4 is a term.
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PROGRAM
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(PARI) a=69; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-1)
(PARI) for(n=0, 1000, if(isprime((620*10^n+1)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103047(n) - 1.
Sequence in context: A006592 A077122 A020540 this_sequence A026740 A130219 A111874
Adjacent sequences: A101537 A101538 A101539 this_sequence A101541 A101542 A101543
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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 06 2004
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