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Search: id:A056254
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| A056254 |
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Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 23 for n > 0. |
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+0
1
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| 1, 7, 139, 229, 425, 461, 725, 1973, 7229, 45859, 47303
(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 (320*10^n - 23)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 5 followed by digit 3 is prime.
Numbers corresponding to terms <= 725 are certified primes. For number corresponding to 1973 see P. De Geest, PDP Reference Table
a(n) = A082707(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 355...553.
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EXAMPLE
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353 is prime, hence 1 is a term.
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PROGRAM
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(PARI) a=33; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a+23)
(PARI) for(n=0, 2000, if(isprime((320*10^n-23)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275, A082707.
Sequence in context: A009701 A120052 A142295 this_sequence A137463 A126156 A082162
Adjacent sequences: A056251 A056252 A056253 this_sequence A056255 A056256 A056257
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KEYWORD
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nonn,hard,base
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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 20 2004
Edited by njas at the suggestion of Andrew Plewe, May 31 2007, Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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