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Search: id:A101150
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| A101150 |
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Indices of primes in sequence defined by A(0) = 79, A(n) = 10*A(n-1) - 21 for n > 0. |
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+0
1
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| 0, 1, 2, 5, 7, 17, 18, 20, 31, 47, 64, 71, 98, 119, 200, 307, 716, 967, 1343, 2131, 3566, 3967, 8326, 10597, 12464, 15874, 18894
(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 (690*10^n + 21)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 6 followed by digit 9 is prime.
Numbers corresponding to terms <= 967 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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7669 is prime, hence 2 is a term.
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PROGRAM
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(PARI) a=79; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-21)
(PARI) for(n=0, 1500, if(isprime((690*10^n+21)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103065(n) - 1.
Sequence in context: A089727 A113514 A067161 this_sequence A038875 A019334 A045356
Adjacent sequences: A101147 A101148 A101149 this_sequence A101151 A101152 A101153
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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 03 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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