1,2

Or number of nonprimes A141468<n. [From Juri-Stepan Gerasimov, Nov 19 2009]

Table of n, a(n) for n=1..74.

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]

Cf. A000027, A000720, A141468. [From Juri-Stepan Gerasimov, Nov 19 2009]

Sequence in context: A035429 A280169 A018117 * A214129 A280151 A094990

Adjacent sequences: A086933 A086934 A086935 * A086937 A086938 A086939

easy,nonn

Zak Seidov, Sep 22 2003

approved