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Search: id:A101139
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| A101139 |
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Indices of primes in sequence defined by A(0) = 71, A(n) = 10*A(n-1) + 31 for n > 0. |
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+0
1
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| 0, 3, 5, 6, 9, 15, 21, 30, 1314, 2063, 6149, 8706
(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 (670*10^n - 31)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 4 followed by digit 1 is prime.
Some of the larger entries may only correspond to probable 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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74441 is prime, hence 3 is a term.
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PROGRAM
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(PARI) a=71; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+31)
(PARI) for(n=0, 1500, if(isprime((670*10^n-31)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103057(n) - 1.
Sequence in context: A072522 A070111 A070117 this_sequence A102606 A102372 A095829
Adjacent sequences: A101136 A101137 A101138 this_sequence A101140 A101141 A101142
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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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