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Search: id:A101969
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| A101969 |
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Indices of primes in sequence defined by A(0) = 21, A(n) = 10*A(n-1) + 71 for n > 0. |
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+0
1
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| 1, 11, 26, 43, 79, 118, 130, 274, 314, 875, 1306
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Numbers n such that (260*10^n - 71)/9 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.
Numbers corresponding to terms <= 875 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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EXAMPLE
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281 is prime, hence 1 is a term.
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PROGRAM
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(PARI) a=21; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+71)
(PARI) for(n=0, 1500, if(isprime((260*10^n-71)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A102960(n) - 1.
Sequence in context: A003345 A047722 A100566 this_sequence A139576 A046806 A027521
Adjacent sequences: A101966 A101967 A101968 this_sequence A101970 A101971 A101972
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KEYWORD
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nonn,hard,more
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004
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