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A101589 Indices of primes in sequence defined by A(0) = 59, A(n) = 10*A(n-1) - 1 for n > 0. 1
0, 3, 7, 12, 15, 43, 438, 607, 1200, 2724, 5209, 59388, 118215, 198528 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that (530*10^n + 1)/9 is prime.

Numbers n such that digit 5 followed by n >= 0 occurrences of digit 8 followed by digit 9 is prime.

Numbers corresponding to terms <= 607 are certified primes.

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 588...889.

Index entries for primes involving repunits.

FORMULA

a(n) = A103024(n) - 1.

EXAMPLE

58889 is prime, hence 3 is a term.

PROG

(PARI) a=59; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-1)

(PARI) for(n=0, 1500, if(isprime((530*10^n+1)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275, A103024.

Sequence in context: A331042 A122981 A122982 * A061559 A165990 A160998

Adjacent sequences:  A101586 A101587 A101588 * A101590 A101591 A101592

KEYWORD

nonn,more

AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

a(12)-a(14) from Kamada data by Ray Chandler, Apr 30 2015

STATUS

approved

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Last modified May 17 21:11 EDT 2021. Contains 343990 sequences. (Running on oeis4.)