1,6

Table of n, a(n) for n=1..91.

Phi(2, 4) = 1: four is a semiprime.

Phi(2, 10) = 3: four, six and ten are semiprimes; nine is a semiprime relatively prime to ten.

Cf. A000010, A144740

Sequence in context: A103863 A166395 A061199 * A103615 A308167 A293665

Adjacent sequences: A144738 A144739 A144740 * A144742 A144743 A144744

easy,nonn

Reikku Kulon, Sep 20 2008

approved