OFFSET
1,2
COMMENTS
Also, numbers k such that 98*10^k - 1 is prime.
Terms from Kamada.
a(9) > 300000.
LINKS
EXAMPLE
For k=0, 9*R_2 - 2*10^0 = 99 - 2 = 97 which is prime.
MATHEMATICA
Select[Range[0, 300000], PrimeQ[98*10^#-1 ] &]
PROG
(Magma) [n: n in [0..300] | IsPrime(98*10^n-1)]; // Vincenzo Librandi, Apr 15 2015
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Apr 14 2015
EXTENSIONS
a(9) from Kamada data by Tyler Busby, May 05 2024
STATUS
approved