OFFSET
1,1
COMMENTS
Also, numbers k such that (10^k - 91)/9 is prime.
Terms from Kamada data.
a(14) > 2.5*10^5.
LINKS
EXAMPLE
For k=3, R_3 - 10 = 111 - 10 = 101 which is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[(10^# - 91)/9] &]
PROG
(Magma) [n: n in [0..1400] | IsPrime((10^n-91) div 9)]; // Vincenzo Librandi, Apr 09 2015
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Apr 08 2015
STATUS
approved