OFFSET
1,2
COMMENTS
Also, numbers k such that 8*10^k - 3 is prime.
Terms from Kamada data.
Note that Kamada does not recognize k=0 as 5 is a degenerate case of form ABB..BBA.
a(15) > 2*10^5.
LINKS
EXAMPLE
For k=2, 9*R_2 + 7*10^k - 2 = 99 + 700 - 2 = 797 which is prime.
MATHEMATICA
Select[Range[0, 200000], PrimeQ[8*10^#-3] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jun 18 2015
STATUS
approved