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A101016 Indices of primes in sequence defined by A(0) = 91, A(n) = 10*A(n-1) + 71 for n > 0. 0
5, 8, 89, 110, 209, 236, 413, 1191, 1259, 5835, 6771 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that (890*10^n - 71)/9 is prime.

Numbers n such that digit 9 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.

Numbers corresponding to terms <= 413 are certified primes.

Certified primality of terms corresponding to 1191 and 1259 with Primo. - Ryan Propper, Jun 20 2005

Next term after 6771 is greater than 10000. - Ryan Propper, Jun 20 2005

REFERENCES

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

9888881 is prime, hence 5 is a term.

PROG

(PARI) a=91; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+71)

(PARI) for(n=0, 1500, if(isprime((890*10^n-71)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275.

a(n) = A103107(n) - 1.

Sequence in context: A213239 A123819 A153720 * A025518 A151827 A162571

Adjacent sequences:  A101013 A101014 A101015 * A101017 A101018 A101019

KEYWORD

nonn,hard,more

AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004

EXTENSIONS

Two additional terms, corresponding to probable primes, from Ryan Propper, Jun 20 2005

Edited by T. D. Noe, Oct 30 2008

STATUS

approved

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Last modified September 1 17:06 EDT 2014. Contains 246309 sequences.