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A101740
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Indices of primes in sequence defined by A(0) = 47, A(n) = 10*A(n-1) + 27 for n > 0.
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0
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0, 14, 40, 63, 130, 137, 191, 286, 494, 965, 1090, 1365, 1713, 1773, 3252, 6330
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OFFSET
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1,2
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COMMENTS
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Numbers n such that (450*10^n - 27)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 9 followed by digit 7 is prime.
Numbers corresponding to terms <= 965 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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LINKS
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Table of n, a(n) for n=1..16.
Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
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4999999999999997 is prime, hence 14 is a term.
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PROG
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(PARI) a=47; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+27)
(PARI) for(n=0, 1500, if(isprime((450*10^n-27)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103003(n) - 1.
Sequence in context: A162266 A181149 A019063 * A069126 A124707 A126368
Adjacent sequences: A101737 A101738 A101739 * A101741 A101742 A101743
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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), Dec 14 2004
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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STATUS
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approved
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