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Search: id:A101008
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| A101008 |
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Indices of primes in sequence defined by A(0) = 97, A(n) = 10*A(n-1) - 23 for n > 0. |
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+0
1
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OFFSET
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1,3
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COMMENT
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Numbers n such that (850*10^n + 23)/9 is a prime.
Numbers n such that digit 9 followed by n >= 0 occurrences of digit 4 followed by digit 7 is a prime.
Numbers corresponding to terms <= 420 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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94447 is a prime, hence 3 is a term.
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PROGRAM
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(PARI) a=97; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-23)
(PARI) for(n=0, 1000, if(isprime((850*10^n + 23)/9), print1(n, ", ")))
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CROSSREFS
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Cf. A000533, A002275.
a(n) = A103099(n) - 1.
Adjacent sequences: A101005 A101006 A101007 this_sequence A101009 A101010 A101011
Sequence in context: A081312 A123598 A106217 this_sequence A070734 A009113 A092468
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KEYWORD
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nonn,hard,more,less
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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 27 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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