A101059 - OEIS

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A101059

Indices of primes in sequence defined by A(0) = 87, A(n) = 10*A(n-1) - 53 for n > 0.

1

2, 8, 16, 152, 193, 640, 674, 1460, 26428, 48460, 72734

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Numbers n such that (730*10^n + 53)/9 is prime.

Numbers n such that digit 8 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.

Numbers corresponding to terms <= 674 are certified primes.

a(12) > 10^5. - Robert Price, Oct 09 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..11.

Makoto Kamada, Prime numbers of the form 811...117.

Index entries for primes involving repunits.

FORMULA

a(n) = A103072(n) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

EXAMPLE

8117 is prime, hence 2 is a term.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(730*10^# + 53)/9] &] (* Robert Price, Oct 09 2015 *)

PROG

(PARI) a=87; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-53)

(PARI) for(n=0, 1500, if(isprime((730*10^n+53)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275, A103072.

Sequence in context: A280777 A013516 A259688 * A191999 A101658 A308613

Adjacent sequences: A101056 A101057 A101058 * A101060 A101061 A101062

KEYWORD

nonn,hard,more

AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004

EXTENSIONS

a(9)-a(10) from Kamada data by Ray Chandler, Apr 29 2015

a(11) from Robert Price, Oct 09 2015

STATUS

approved