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A101527
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Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) + 31 for n > 0.
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0
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0, 1, 6, 18, 24, 36, 48, 132, 612, 1339, 2035, 2490, 26262
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that (580*10^n - 31)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 4 followed by digit 1 is prime.
Numbers corresponding to terms <= 612 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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FORMULA
| a(n) = A103034(n) - 1.
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EXAMPLE
| 641 is prime, hence 1 is a term.
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PROG
| (PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+31)
(PARI) for(n=0, 1500, if(isprime((580*10^n-31)/9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
Sequence in context: A081318 A011775 A015707 * A028887 A051395 A028558
Adjacent sequences: A101524 A101525 A101526 * A101528 A101529 A101530
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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
| Two more terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 22 2007
a(13) from Max Alekseyev (maxale(AT)gmail.com), Dec 12 2011
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