

A259127


Numbers k such that 8*R_k + 3*10^k  5 is prime, where R_k = 11...11 is the repunit (A002275) of length k.


0



2, 12, 30, 60, 116, 290, 632, 1064, 1494, 5432, 7362
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

Also, numbers k such that (35*10^n  53)/9 is prime.
Terms from Kamada data.
a(12) > 10^5.


LINKS

Table of n, a(n) for n=1..11.
Makoto Kamada, Nearrepdigit numbers of the form ABB...BBA.
Makoto Kamada, Prime numbers of the form 388...883.
Index entries for primes involving repunits.


EXAMPLE

For k=2, 8*R_2 + 3*10^k  5 = 88 + 300  5 = 383 which is prime.


MATHEMATICA

Select[Range[100000], PrimeQ[(35*10^#53)/9] &] (* adapted by Vincenzo Librandi, Jun 19 2015 *)


CROSSREFS

Cf. A002275.
Sequence in context: A118239 A249055 A127118 * A296257 A301774 A286230
Adjacent sequences: A259124 A259125 A259126 * A259128 A259129 A259130


KEYWORD

more,hard,nonn


AUTHOR

Robert Price, Jun 18 2015


EXTENSIONS

Corrected Mathematica code from Vincenzo Librandi, Jun 19 2015


STATUS

approved



