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A101951
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Indices of primes in sequence defined by A(0) = 23, A(n) = 10*A(n-1) - 27 for n > 0.
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1
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0, 2, 4, 5, 6, 11, 15, 16, 21, 23, 34, 114, 119, 357, 1487, 1818, 4678, 9820
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Numbers n such that 20*10^n + 3 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 0 followed by digit 3 is prime.
Numbers corresponding to terms <= 357 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
| 2003 is prime, hence 2 is a term.
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PROG
| (PARI) a=23; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-27)
(PARI) for(n=0, 1500, if(isprime(20*10^n+3), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A081677(n) - 1.
Sequence in context: A113631 A202101 A192582 * A171166 A194607 A194637
Adjacent sequences: A101948 A101949 A101950 * A101952 A101953 A101954
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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 23 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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