OFFSET
1,2
COMMENTS
Also, numbers k such that (10^k + 359)/9 is prime.
Terms from Kamada data. Note that Kamada does not recognize k=1 as 41 is a degenerate case of form AAA..ABA.
a(21) > 10^6.
LINKS
EXAMPLE
For k=3, R_3 + 40 = 111 + 40 = 151 which is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[(10^# + 359)/9] &]
PROG
(Magma) [n: n in [1..400] | IsPrime((10^n+359) div 9)]; // Vincenzo Librandi, Apr 10 2015
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Apr 09 2015
STATUS
approved