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Search: id:A101849
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| A101849 |
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Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n-1) + 27 for n > 0. |
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1
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OFFSET
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1,3
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COMMENT
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Numbers n such that (360*10^n - 27)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 9 followed by digit 7 is prime.
Numbers corresponding to terms <= 871 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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Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
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397 is prime, hence 1 is a term.
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PROGRAM
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(PARI) a=37; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+27)
(PARI) for(n=0, 1500, if(isprime((360*10^n-27)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A101398(n) - 1.
Sequence in context: A005106 A050265 A120140 this_sequence A141562 A108097 A102764
Adjacent sequences: A101846 A101847 A101848 this_sequence A101850 A101851 A101852
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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 20 2004
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EXTENSIONS
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8845 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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