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Search: id:A101072
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| A101072 |
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Indices of primes in sequence defined by A(0) = 87, A(n) = 10*A(n-1) - 13 for n > 0. |
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1
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OFFSET
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1,2
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COMMENT
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Numbers n such that (770*10^n + 13)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 5 followed by digit 7 is prime.
Some of the larger entries may only correspond to probable 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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855555557 is prime, hence 7 is a term.
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PROGRAM
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(PARI) a=87; for(n=0, 2300, if(isprime(a), print1(n, ", ")); a=10*a-13)
(PARI) for(n=0, 2300, if(isprime((770*10^n+13)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103085(n) - 1.
Sequence in context: A110718 A004807 A139781 this_sequence A144927 A159994 A119181
Adjacent sequences: A101069 A101070 A101071 this_sequence A101073 A101074 A101075
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KEYWORD
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nonn,bref,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), Nov 30 2004
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