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A100998
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Indices of primes in sequence defined by A(0) = 97, A(n) = 10*A(n-1) - 63 for n > 0.
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0
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0, 1, 2, 3, 4, 14, 18, 19, 45, 51, 52, 191, 379, 587, 775, 905, 1349, 1735, 2913, 7507, 15709, 16452, 17487, 18108
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that 90*10^n + 7 is prime.
Numbers n such that digit 9 followed by n >= 0 occurrences of digit 0 followed by digit 7 is prime.
Numbers corresponding to terms <= 1349 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
| 90007 is prime, hence 3 is a term.
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PROG
| (PARI) a=97; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-63)
(PARI) for(n=0, 1500, if(isprime(90*10^n+7), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A096774(n) - 1.
Sequence in context: A103048 A140128 A167906 * A127283 A047193 A019137
Adjacent sequences: A100995 A100996 A100997 * A100999 A101000 A101001
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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), Nov 27 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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