OFFSET
1,1
COMMENTS
Also, numbers k such that (10^k + 179)/9 is prime.
Terms from Kamada data.
a(27) > 2.5*10^5.
LINKS
EXAMPLE
For k=3, R_3 + 20 = 111 + 20 = 131 which is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[(10^# + 179)/9] &]
PROG
(Magma) [n: n in [1..400] | IsPrime((10^n+179) div 9)]; // Vincenzo Librandi, Apr 10 2015
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Apr 09 2015
STATUS
approved