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A101569
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Indices of primes in sequence defined by A(0) = 59, A(n) = 10*A(n-1) - 81 for n > 0.
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0
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0, 1, 2, 4, 7, 19, 28, 85, 282, 756, 1198, 2472, 2732
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that 50*10^n + 9 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 0 followed by digit 9 is prime.
Numbers corresponding to terms <= 756 are certified primes.
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REFERENCES
| Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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LINKS
| Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
| 500009 is prime, hence 4 is a term.
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PROG
| (PARI) a=59; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-81)
(PARI) for(n=0, 1500, if(isprime(50*10^n+9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A103004(n) - 1.
Sequence in context: A076894 A047871 A103032 * A101805 A145777 A188497
Adjacent sequences: A101566 A101567 A101568 * A101570 A101571 A101572
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KEYWORD
| nonn,more
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AUTHOR
| 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
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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