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A101128
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Indices of primes in sequence defined by A(0) = 71, A(n) = 10*A(n-1) - 9 for n > 0.
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0
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0, 1, 2, 3, 4, 7, 8, 44, 135, 141, 157, 242, 922, 1234, 2195, 4649, 6118, 7323, 9542, 13493
(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 + 1 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime.
Numbers corresponding to terms <= 922 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
| 700001 is prime, hence 4 is a term.
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PROG
| (PARI) a=71; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-9)
(PARI) for(n=0, 1500, if(isprime(70*10^n+1), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A056804(n) - 1.
Sequence in context: A126882 A006549 A159554 * A182802 A172024 A119345
Adjacent sequences: A101125 A101126 A101127 * A101129 A101130 A101131
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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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