OFFSET
1,1
COMMENTS
Also numbers k such that 10^(k+1) - 9 is a prime.
LINKS
FORMULA
a(n) = A095714(n) - 1.
MATHEMATICA
Do[ If[ PrimeQ[90*(10^n - 1)/9 + 1], Print[n]], {n, 0, 7000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Aug 10 2000
EXTENSIONS
a(15) - a(16) from Jason Earls, Jan 07 2008
a(17) - a(19) from Alexander Gramolin, May 13 2011
Edited by Ray Chandler, Feb 26 2012
STATUS
approved