OFFSET
1,2
COMMENTS
Also, numbers k such that (163*10^k - 1)/9 is prime.
Terms from Kamada.
a(16) > 250000.
LINKS
EXAMPLE
For k=2, R_4 + 7*10^2 = 1111 + 700 = 1811 which is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[(163*10^#-1)/9 ] &]
PROG
(Magma) [n: n in [0..300] | IsPrime((163*10^n-1) div 9)]; // Vincenzo Librandi, Apr 14 2015
(PARI) for(n=0, 300, if(isprime((163*10^n-1)/9), print1(n, ", "))) \\ Derek Orr, Apr 14 2015
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Apr 13 2015
STATUS
approved