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Search: id:A101061
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| A101061 |
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Indices of primes in sequence defined by A(0) = 81, A(n) = 10*A(n-1) + 11 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 (740*10^n - 11)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 2 followed by digit 1 is prime.
Numbers corresponding to terms <= 176 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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Makoto Kamada, Factorizations of near-repdigit numbers.
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FORMULA
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a(n) = A103074(n) - 1. - 8461 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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EXAMPLE
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822221 is prime, hence 4 is a term.
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PROGRAM
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(PARI) a=81; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a+11)
(PARI) for(n=0, 1000, if(isprime((740*10^n-11)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
Sequence in context: A133465 A110128 A148279 this_sequence A148280 A112638 A077162
Adjacent sequences: A101058 A101059 A101060 this_sequence A101062 A101063 A101064
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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), Nov 30 2004
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EXTENSIONS
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8461 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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