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A101534
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Indices of primes in sequence defined by A(0) = 69, A(n) = 10*A(n-1) - 31 for n > 0.
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0
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1, 4, 7, 16, 19, 64, 82, 89, 107, 251, 334, 1487, 6355
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Numbers n such that (590*10^n + 31)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 5 followed by digit 9 is prime.
Numbers corresponding to terms <= 334 are certified primes.
Next term, if exists, is bigger than 3000. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Feb 03 2006
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REFERENCES
| Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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LINKS
| Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
| 655559 is prime, hence 4 is a term.
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MATHEMATICA
| For[n=1, n<= 3000, n++, If[PrimeQ[(590*10^n + 31)/9], Print[n]]] (Steinerberger)
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PROG
| (PARI) a=69; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-31)
(PARI) for(n=0, 1500, if(isprime((590*10^n+31)/9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A103041(n) - 1.
Sequence in context: A160715 A160120 A130665 * A110933 A067398 A054599
Adjacent sequences: A101531 A101532 A101533 * A101535 A101536 A101537
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KEYWORD
| nonn,hard,more
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AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004
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EXTENSIONS
| More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Feb 03 2006
6355 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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