OFFSET
1,1
COMMENTS
Also numbers k such that (4*10^(k+1) + 41)/9 is prime.
a(11) > 10^5. - Robert Price, Nov 09 2014
LINKS
FORMULA
a(n) = A099414(n+1) - 1. - Robert Price, Nov 09 2014
MATHEMATICA
Do[ If[ PrimeQ[40*(10^n - 1)/9 + 9], Print[n]], {n, 5000}]
PROG
(Magma) [n: n in [0..300] | IsPrime((4*10^(n+1)+41)div 9)]; Vincenzo Librandi, Nov 10 2014
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2000
EXTENSIONS
a(8)-a(10) derived from A099414 by Robert Price, Nov 09 2014
STATUS
approved