OFFSET
1,2
COMMENTS
Also, numbers k such that (10^k + 89)/9 is prime.
Terms from Kamada data. Note Kamada does not recognize k=1 as 11 is a degenerate case of form AAA..ABA.
a(12) > 10^6.
LINKS
EXAMPLE
For k=6, R_6 + 10 = 111111 + 10 = 111121 which is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[(10^# + 89)/9] &]
PROG
(Magma) [n: n in [1..400] | IsPrime((10^n+89) div 9)]; // Vincenzo Librandi, Apr 10 2015
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Apr 09 2015
STATUS
approved