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Search: id:A101848
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| A101848 |
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Indices of primes in sequence defined by A(0) = 31, A(n) = 10*A(n-1) + 81 for n > 0. |
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+0
1
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| 0, 16, 18, 28, 42, 118, 172, 948, 1608, 5578, 19678
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Numbers n such that (360*10^n - 81)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 9 followed by digit 1 is prime.
Numbers corresponding to terms <= 948 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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31 is prime, hence 0 is a term.
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PROGRAM
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(PARI) a=31; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+81)
(PARI) for(n=0, 1500, if(isprime((360*10^n-81)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A101396(n) - 1.
Sequence in context: A081258 A057369 A117100 this_sequence A032401 A070574 A034012
Adjacent sequences: A101845 A101846 A101847 this_sequence A101849 A101850 A101851
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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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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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