OFFSET
1,1
COMMENTS
Also, numbers k such that (10^k + 719)/9 is prime.
Terms from Kamada data.
a(15) > 2.5*10^5.
LINKS
EXAMPLE
For k=3, R_3 + 80 = 111 + 80 = 191 which is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[(10^# + 719)/9] &]
PROG
(Magma) [n: n in [2..300] | IsPrime((10^n+719) div 9)]; // Vincenzo Librandi, Apr 10 2015
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Apr 09 2015
STATUS
approved