This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A144741 #18 Apr 15 2023 06:21:55 %S A144741 0,0,0,1,0,2,0,2,2,3,0,4,0,4,4,4,0,6,0,5,5,5,0,8,3,6,4,7,0,10,0,6,6,7, %T A144741 6,11,0,8,7,11,0,14,0,9,9,9,0,14,4,12,8,10,0,15,7,12,9,10,0,20,0,11, %U A144741 11,11,8,19,0,12,10,18,0,19,0,12,14,13,8,21,0,17,9,13,0,24,9,14,11,17,0,28,9 %N A144741 Number of semiprimes less than or equal to and not coprime to n. %e A144741 a(10) = 3: four, six and ten are semiprimes; nine is a semiprime relatively prime to ten. %o A144741 (PARI) a(n) = sum(k=1, n, if (bigomega(k) == 2, gcd(k,n) != 1)); \\ _Michel Marcus_, Apr 15 2023 %Y A144741 Cf. A000010, A001358, A144740. %K A144741 easy,nonn %O A144741 1,6 %A A144741 _Reikku Kulon_, Sep 20 2008