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Search: id:A056257
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| A056257 |
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Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) - 43 for n > 0. |
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+0
1
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OFFSET
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1,2
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COMMENT
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Numbers n such that (650*10^n + 43)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 2 followed by digit 7 is prime.
Numbers corresponding to terms <= 723 are certified primes. For number corresponding to 1785 see P. De Geest, PDP Reference Table.
a(n) = A082711(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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P. De Geest, PDP Reference Table
Makoto Kamada, Factorizations of 722...227.
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EXAMPLE
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72227 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-43)
(PARI) for(n=0, 1000, if(isprime((650*10^n+43)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275, A082711.
Adjacent sequences: A056254 A056255 A056256 this_sequence A056258 A056259 A056260
Sequence in context: A120120 A126472 A019059 this_sequence A066021 A098465 A081562
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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 njas at the suggestion of Andrew Plewe, Jun 08 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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