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Search: id:A101731
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| A101731 |
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Indices of primes in sequence defined by A(0) = 47, A(n) = 10*A(n-1) - 3 for n > 0. |
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+0
1
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| 0, 1, 5, 9, 11, 12, 21, 31, 45, 60, 67, 89, 109, 651, 1607, 1903, 2002, 3037, 3085, 9579, 9697
(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 (420*10^n + 3)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 6 followed by digit 7 is prime.
Numbers corresponding to terms <= 651 are certified primes.
a(n) = A099017(n-1) - 1.
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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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467 is prime, hence 1 is a term.
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PROGRAM
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(PARI) a=47; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-3)
(PARI) for(n=0, 1500, if(isprime((420*10^n+3)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275, A099017.
Sequence in context: A131634 A049049 A118358 this_sequence A080765 A043721 A043727
Adjacent sequences: A101728 A101729 A101730 this_sequence A101732 A101733 A101734
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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 14 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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