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A101531
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Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) + 41 for n > 0.
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0
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0, 2, 3, 9, 21, 39, 53, 80, 83, 105, 192, 596, 680, 1362, 1875, 4023
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OFFSET
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1,2
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COMMENTS
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Numbers n such that (590*10^n - 41)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 5 followed by digit 1 is prime.
Numbers corresponding to terms <= 680 are certified primes.
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REFERENCES
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Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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LINKS
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Table of n, a(n) for n=1..16.
Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
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65551 is prime, hence 3 is a term.
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PROG
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(PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+41)
(PARI) for(n=0, 1500, if(isprime((590*10^n-41)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103038(n) - 1.
Sequence in context: A111189 A001004 A015951 * A099607 A077550 A056780
Adjacent sequences: A101528 A101529 A101530 * A101532 A101533 A101534
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KEYWORD
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nonn,hard,more
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AUTHOR
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Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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STATUS
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approved
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