A101588 Indices of primes in sequence defined by A(0) = 57, A(n) = 10*A(n-1) + 17 for n > 0.

1, 5, 7, 19, 107, 287, 305, 461, 20101, 30041, 69049

Offset

1,2

Comments

Numbers n such that (530*10^n - 17)/9 is prime.

Numbers n such that digit 5 followed by n >= 0 occurrences of digit 8 followed by digit 7 is prime.

Numbers corresponding to terms <= 461 are certified primes.

a(12) > 10^5. - Robert Price, Sep 07 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 588...887.

Index entries for primes involving repunits.

Formula

a(n) = A103023(n) - 1.

Example

587 is prime, hence 1 is a term.

Mathematica

Select[Range[0, 300], PrimeQ[(530*10^# - 17)/9] &] (* Robert Price, Sep 07 2015 *)

Prog

(PARI) a=57; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a+17)
(PARI) for(n=0, 1000, if(isprime((530*10^n-17)/9), print1(n, ", ")))
(Magma) [n: n in [0..350] | IsPrime((530*10^n-17) div 9 )]; // Vincenzo Librandi, Sep 08 2015

Crossrefs

Cf. A000533, A002275, A103023.

Sequence in context: A229065 A171131 A096636 * A288405 A280150 A062654

Adjacent sequences: A101585 A101586 A101587 * A101589 A101590 A101591

Keyword

nonn,more

Author

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

Extensions

a(9)-a(10) from Kamada data by Ray Chandler, Apr 30 2015

a(11) from Robert Price, Sep 07 2015

Status

approved