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Search: id:A101066
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| A101066 |
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Indices of primes in sequence defined by A(0) = 81, A(n) = 10*A(n-1) + 31 for n > 0. |
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+0
1
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| 25, 35, 37, 59, 79, 91, 173, 485, 626, 998, 1613, 4381, 4897, 8441
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Numbers n such that (760*10^n - 31)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 4 followed by digit 1 is prime.
Numbers corresponding to terms <= 626 are certified primes.
Next term after 4897 is greater than 10000. - Ryan Propper (rpropper(AT)stanford.edu), Jun 20 2005
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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) = A103079(n) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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EXAMPLE
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844444444444444444444444441 is prime, hence 25 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+31)
(PARI) for(n=0, 1000, if(isprime((760*10^n-31)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
Adjacent sequences: A101063 A101064 A101065 this_sequence A101067 A101068 A101069
Sequence in context: A075452 A020258 A098368 this_sequence A061442 A049514 A049518
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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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Three additional terms, corresponding to pseudoprimes, from Ryan Propper (rpropper(AT)stanford.edu), Jun 20 2005
One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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