%I #13 Sep 02 2013 12:31:52
%S 0,2,6,8,13,16,22,26,34,39,48,55,62,75,82,89,103,113,126,135,149,163,
%T 179,190,202,220,236,252,270,288,304,320,340,360,381,403,425,443,462,
%U 483,508,532,556,581,604,633,655,678,709,738,761,782
%N Number of prime pairs {p,q}, such that pq < n^2.
%C Number of semiprimes (A001358) < n^2. [_Michel Marcus_, Sep 02 2013]
%e a(3)=2 because only the prime pairs (2,2) and (2,3) form products < 9.
%o (PARI) a(n) = {sqn = n^2; idp = primepi(sqn\2); nbp = 0; for (i = 1, idp, p = prime(i); for (j = 1, i, if (p * prime(j) < sqn, nbp++););); nbp;} \\ _Michel Marcus_, Sep 02 2013
%Y Cf. A205726.
%K nonn
%O 2,2
%A Joe K. Crump (joecr(AT)carolina.rr.com)