OFFSET
1,2
COMMENTS
Also numbers k such that (2*10^(k+1)+61)/9 is prime.
a(14) > 10^5. - Robert Price, Nov 01 2014
LINKS
FORMULA
a(n) = A099410(n+1) - 1. - Robert Price, Nov 01 2014
MATHEMATICA
Do[ If[ PrimeQ[20*(10^n - 1)/9 + 9], Print[n]], {n, 5000}]
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2000
EXTENSIONS
Two more terms from Rick L. Shepherd, Mar 30 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(11)-a(13) derived from A099410 by Robert Price, Nov 01 2014
STATUS
approved