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A102010 Indices of primes in sequence defined by A(0) = 17, A(n) = 10*A(n-1) - 43 for n > 0. 1
0, 1, 3, 13, 24, 31, 55, 61, 810, 811, 1083, 2532, 11923, 49551 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Numbers n such that (110*10^n + 43)/9 is prime.

Numbers n such that digit 1 followed by n >= 0 occurrences of digit 2 followed by digit 7 is prime.

Numbers corresponding to terms <= 811 are certified primes.

a(15) > 10^5. - Robert Price, Jan 16 2015

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..14.

Makoto Kamada, Prime numbers of the form 122...227.

Index entries for primes involving repunits.

FORMULA

a(n) = A102930(n) - 1.

EXAMPLE

12227 is prime, hence 3 is a term.

PROG

(PARI) a=17; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-43)

(PARI) for(n=0, 1500, if(isprime((110*10^n+43)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275, A102930.

Sequence in context: A133313 A230026 A260798 * A121718 A261599 A144826

Adjacent sequences:  A102007 A102008 A102009 * A102011 A102012 A102013

KEYWORD

nonn,hard,more

AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(13)-a(14) derived from A102930 by Robert Price, Jan 16 2015

STATUS

approved

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Last modified October 14 09:25 EDT 2019. Contains 327995 sequences. (Running on oeis4.)