OFFSET
1,2
COMMENTS
Also, numbers k such that (82*10^k + 71)/9 is prime.
Terms from Kamada data.
Note Kamada does not recognize k=0 as 17 is a degenerate case of form ABB..BBA.
a(7) > 10^5.
LINKS
EXAMPLE
For k=2, R_2 + 9*10^k + 8 = 11 + 900 + 8 = 919 which is prime.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(82*10^#+71)/9] &]
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Jun 18 2015
STATUS
approved