OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n)=primepi(A049097(n))
MATHEMATICA
Select[Range[200], SquareFreeQ[Prime[#]+1]&] (* Harvey P. Dale, Sep 07 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Aug 15 2006
STATUS
approved