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Search: id:A101155
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| A101155 |
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Indices of primes in sequence defined by A(0) = 73, A(n) = 10*A(n-1) + 63 for n > 0. |
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+0
1
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| 0, 2, 4, 5, 9, 11, 12, 38, 47, 53, 63, 81, 146, 147, 359, 398, 1637, 1875, 2145, 2193
(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 (720*10^n - 63)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 9 followed by digit 3 is prime.
Numbers corresponding to terms <= 398 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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EXAMPLE
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7999993 is prime, hence 5 is a term.
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PROGRAM
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(PARI) a=73; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a+63)
(PARI) for(n=0, 1000, if(isprime((720*10^n-63)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A099190(n) - 1.
Sequence in context: A098845 A069001 A047378 this_sequence A065825 A124254 A065514
Adjacent sequences: A101152 A101153 A101154 this_sequence A101156 A101157 A101158
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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 03 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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