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A102019
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Indices of primes in sequence defined by A(0) = 13, A(n) = 10*A(n-1) + 23 for n > 0.
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0
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OFFSET
| 1,2
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COMMENTS
| Numbers n such that (140*10^n - 23)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 5 followed by digit 3 is prime.
Numbers corresponding to terms <= 75 are certified primes. No further terms up to 3100.
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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
| 1553 is prime, hence 2 is a term.
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PROG
| (PARI) a=13; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+23)
(PARI) for(n=0, 1500, if(isprime((140*10^n-23)/9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A102936(n) - 1.
Sequence in context: A049082 A158095 A059958 * A097595 A081483 A118478
Adjacent sequences: A102016 A102017 A102018 * A102020 A102021 A102022
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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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