OFFSET
1,1
COMMENTS
Also, numbers k such that (7*10^k + 173)/9 is prime.
Terms from Kamada.
a(23) > 200000. - Tyler Busby, Apr 20 2024
LINKS
EXAMPLE
For k=3, 7*R_11 + 20 = 777 + 20 = 797 which is prime.
MATHEMATICA
Select[Range[0, 30000], PrimeQ[(7*10^# + 173)/9] &]
PROG
(Magma) [n: n in [0..400] | IsPrime((7*10^n + 173) div 9)]; // Vincenzo Librandi, Apr 13 2015
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Apr 12 2015
EXTENSIONS
a(18)-a(22) from Kamada data by Tyler Busby, Apr 20 2024
STATUS
approved