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Search: id:A101073
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| A101073 |
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Indices of primes in sequence defined by A(0) = 89, A(n) = 10*A(n-1) - 31 for n > 0. |
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+0
1
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| 0, 1, 7, 16, 18, 24, 39, 48, 57, 58, 91, 112, 295, 636, 1855, 2514, 3592, 6990
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Numbers n such that (770*10^n + 31)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 5 followed by digit 9 is prime.
Numbers corresponding to terms <= 636 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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855555559 is prime, hence 7 is a term.
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PROGRAM
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(PARI) a=89; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-31)
(PARI) for(n=0, 1000, if(isprime((770*10^n+31)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103086(n) - 1.
Sequence in context: A101681 A067776 A132348 this_sequence A026226 A060914 A044059
Adjacent sequences: A101070 A101071 A101072 this_sequence A101074 A101075 A101076
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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), Nov 30 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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