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Search: id:A101952
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| A101952 |
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Indices of primes in sequence defined by A(0) = 29, A(n) = 10*A(n-1) - 81 for n > 0. |
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+0
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 20*10^n + 9 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 0 followed by digit 9 is prime.
Numbers corresponding to terms <= 760 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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200009 is prime, hence 4 is a term.
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PROGRAM
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(PARI) a=29; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-81)
(PARI) for(n=0, 1500, if(isprime(20*10^n+9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A101392(n) - 1.
Sequence in context: A024250 A010572 A012945 this_sequence A009535 A139096 A111425
Adjacent sequences: A101949 A101950 A101951 this_sequence A101953 A101954 A101955
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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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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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