OFFSET
1,2
COMMENTS
Or number of nonprimes A141468<n. [From Juri-Stepan Gerasimov, Nov 19 2009]
FORMULA
a(n)=sum{k=0..n, (1+mu(if(prime(k), k, 1)))/2} [offset 0] - Paul Barry, May 10 2005
a(n)=1+n-A000720(n). [From Juri-Stepan Gerasimov, Nov 19 2009]
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Sep 22 2003
STATUS
approved