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A101130
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Indices of primes in sequence defined by A(0) = 79, A(n) = 10*A(n-1) - 81 for n > 0.
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0
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0, 1, 3, 5, 10, 11, 12, 34, 45, 56, 127, 155, 262, 352, 395, 428, 782, 981, 1057, 1562, 1694, 1815, 1936, 4235, 4430, 6857, 9897
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that 70*10^n + 9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 0 followed by digit 9 is prime.
Numbers corresponding to terms <= 981 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
| 70009 is prime, hence 3 is a term.
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PROG
| (PARI) a=79; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-81)
(PARI) for(n=0, 1500, if(isprime(70*10^n+9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A097954(n) - 1.
Sequence in context: A069193 A078430 A113858 * A191513 A102309 A067230
Adjacent sequences: A101127 A101128 A101129 * A101131 A101132 A101133
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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 03 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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