OFFSET
1,1
COMMENTS
Also, numbers k such that (67*10^k + 23)/9 is prime.
Terms from Kamada data.
a(12) > 10^5.
LINKS
EXAMPLE
For k=10, 4*R_2 + 7*10^k + 3 = 4444444444 + 7000000000 + 3 = 74444444447 which is prime.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(67*10^#+23)/9] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jun 18 2015
STATUS
approved