OFFSET
1,1
COMMENTS
Also, numbers k such that (29*10^k + 7)/9 is prime.
Terms from Kamada data.
a(7) > 10^5.
LINKS
EXAMPLE
For k=6, 2*R_6 + 3*10^k + 1 = 222222 + 3000000 + 1 = 3222223 which is prime.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(29*10^#+7)/9] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jun 18 2015
STATUS
approved