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Search: id:A056245
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| A056245 |
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Indices of primes in sequence defined by A(0) = 11, A(n) = 10*A(n-1) + 31 for n > 0. |
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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 (130*10^n - 31)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 4 followed by digit 1 is prime.
Numbers corresponding to terms <= 65 are certified primes. For number corresponding to 1253 see P. De Geest, PDP Reference Table.
a(n) = A082698(n-2) - 2 for n > 1.
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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 144...441.
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EXAMPLE
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1444441 is prime, hence 5 is a term.
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PROGRAM
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(PARI) a=11; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+31)
(PARI) for(n=0, 1500, if(isprime((130*10^n-31)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275, A082698.
Adjacent sequences: A056242 A056243 A056244 this_sequence A056246 A056247 A056248
Sequence in context: A103974 A006278 A121822 this_sequence A079482 A147625 A157097
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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 28 2004
Edited by N. J. A. Sloane (njas(AT)research.att.com), Jun 15 2007
8405 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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