OFFSET
1,2
COMMENTS
Also, numbers k such that (17*10^k - 71)/9 is prime.
Terms from Kamada data.
a(13) > 10^5.
LINKS
EXAMPLE
For k=8, 8*R_8 + 10^k - 7 = 88888888 + 100000000 - 7 = 188888881 which is prime.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(17*10^#-71)/9] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jun 18 2015
STATUS
approved