OFFSET
1,2
MATHEMATICA
a[n_]:=Length[Select[Range[0, Floor[1/30*(-7+10^n)]], PrimeQ[30*#+7]&]]
a/@Range[1, 7] (* Julien Kluge, Sep 20 2016 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert G. Wilson v, Jan 12 2004
EXTENSIONS
a(11)-a(13) from Hiroaki Yamanouchi, Oct 14 2014
STATUS
approved