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A101517
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Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) - 9 for n > 0.
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0
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0, 1, 7, 8, 14, 19, 25, 37, 44, 64, 111, 243, 302, 392, 559, 838, 1008, 1018, 1172, 1333, 2235, 2628, 4425, 8847, 20811
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that 60*10^n + 1 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime.
Numbers corresponding to terms <= 838 are certified primes.
Certified primality of numbers corresponding to terms 1008,1018,1172,1333 with Primo. - Ryan Propper (rpropper(AT)stanford.edu), Jun 20 2005
There are no other numbers < 2150. - Stefan Steinerberger (hansibal(AT)hotmail.com), Nov 06 2005
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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 600...001.
Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
| 600000001 is prime, hence 7 is a term.
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PROG
| (PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-9)
(PARI) for(n=0, 1500, if(isprime(60*10^n+1), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A056805(n) - 1.
Sequence in context: A047274 A037368 A037970 * A015893 A165465 A047521
Adjacent sequences: A101514 A101515 A101516 * A101518 A101519 A101520
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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 06 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm) and Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 28 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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