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Search: id:A056259
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| A056259 |
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Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) - 13 for n > 0. |
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+0
1
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| 1, 3, 9, 19, 21, 57, 73, 81, 207, 349, 421, 3811, 3981, 20923, 23785, 38851
(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 (680*10^n + 13)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 5 followed by digit 7 is prime.
Numbers corresponding to terms <= 421 are certified primes.
a(n) = A082713(n-1) - 2.
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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 755...557.
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EXAMPLE
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75557 is prime, hence 3 is a term.
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PROGRAM
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(PARI) a=77; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-13)
(PARI) for(n=0, 1000, if(isprime((680*10^n+13)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275, A082713.
Sequence in context: A043097 A084670 A002091 this_sequence A056682 A032670 A068677
Adjacent sequences: A056256 A056257 A056258 this_sequence A056260 A056261 A056262
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KEYWORD
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nonn,hard,more
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 18 2000
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EXTENSIONS
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Additional comments from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 03 2004
Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion of Andrew Plewe, Jun 05 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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