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Search: id:A101580
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| A101580 |
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Indices of primes in sequence defined by A(0) = 57, A(n) = 10*A(n-1) - 23 for n > 0. |
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1
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| 1, 5, 7, 17, 52, 67, 241, 275, 319, 563, 619, 1781, 2339, 2453, 5764
(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 (490*10^n + 23)/9 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 4 followed by digit 7 is prime.
Numbers corresponding to terms <= 619 are certified primes.
Next term after 2453 is greater than 5000. - Ryan Propper (rpropper(AT)stanford.edu), Jun 18 2005
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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 544...447.
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EXAMPLE
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547 is prime, hence 1 is a term.
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PROGRAM
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(PARI) a=57; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-23)
(PARI) for(n=0, 1000, if(isprime((490*10^n+23)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103015(n) - 1.
Sequence in context: A030785 A019404 A079604 this_sequence A123195 A145582 A034762
Adjacent sequences: A101577 A101578 A101579 this_sequence A101581 A101582 A101583
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KEYWORD
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nonn,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 09 2004
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EXTENSIONS
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Three additional terms, corresponding to probable primes, from Ryan Propper (rpropper(AT)stanford.edu), Jun 18 2005
5764 from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007
Edited by T. D. Noe (noe(AT)sspectra.com), Oct 30 2008
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