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A102034
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Indices of primes in sequence defined by A(0) = 17, A(n) = 10*A(n-1) + 27 for n > 0.
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0
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0, 1, 2, 3, 12, 13, 75, 236, 871, 987, 1279, 1369, 2685, 3611, 4050, 4644, 9161
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that (180*10^n - 27)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 9 followed by digit 7 is prime.
Numbers corresponding to terms <= 987 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
| 197 is prime, hence 1 is a term.
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PROG
| (PARI) a=17; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+27)
(PARI) for(n=0, 1500, if(isprime((180*10^n-27)/9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A102947(n) - 1.
Sequence in context: A102660 A081347 A074347 * A102150 A039588 A024579
Adjacent sequences: A102031 A102032 A102033 * A102035 A102036 A102037
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KEYWORD
| nonn,hard,more
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AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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