OFFSET
1,2
COMMENTS
Also numbers k such that (5*10^(k+1)+13)/9 is prime.
a(16) > 10^5. - Robert Price, Nov 01 2014
LINKS
FORMULA
a(n) = A099417(n+1) - 1. - Robert Price, Nov 01 2014
MATHEMATICA
Do[ If[ PrimeQ[50*(10^n - 1)/9 + 7], Print[n]], {n, 0, 5000}]
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2000
EXTENSIONS
a(13)-a(15) derived from A099417 by Robert Price, Nov 01 2014
STATUS
approved