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A102008
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Indices of primes in sequence defined by A(0) = 19, A(n) = 10*A(n-1) - 81 for n > 0.
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0
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0, 1, 2, 3, 8, 17, 21, 44, 48, 55, 68, 145, 201, 271, 2729, 2840, 4561, 31809, 43185, 48108
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that 10*10^n + 9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 0 followed by digit 9 is prime.
Numbers corresponding to terms <= 271 are certified primes.
a(n) = A088275(n-1) - 1.
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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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EXAMPLE
| 1009 is prime, hence 2 is a term.
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PROG
| (PARI) a=19; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-81)
(PARI) for(n=0, 1500, if(isprime(10*10^n + 9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275, A088275.
Sequence in context: A185171 A005648 A113947 * A200083 A158921 A064954
Adjacent sequences: A102005 A102006 A102007 * A102009 A102010 A102011
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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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