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 A101041 #10 Feb 16 2024 14:47:28
%S A101041 1,2,3,4,5,6,7,7,8,9,10,10,11,12,13,13,14,14,15,15,16,17,18,18,19,20,
%T A101041 20,20,21,21,22,22,23,24,25,25,26,27,28,28,29,29,30,30,30,31,32,32,33,
%U A101041 33,34,34,35,35,36,36,37,38,39,39,40,41,41,41,42,42,43,43,44,44,45,45,46
%N A101041 Number of numbers not greater than n having no more than two prime factors.
%C A101041 a(n) = 1 + Sum_{k=1..n} A101040(k);
%C A101041 asymptotically: a(n) ~ n*log(log(n))/log(n).
%C A101041 Primes counted with multiplicity. - _Harvey P. Dale_, Feb 16 2024
%F A101041 a(n) = A000720(n) + A072000(n) + 1.
%t A101041 Accumulate[Table[If[PrimeOmega[n]<3,1,0],{n,80}]] (* _Harvey P. Dale_, Feb 16 2024 *)
%Y A101041 Cf. A000720, A072000, A101040.
%K A101041 nonn
%O A101041 1,2
%A A101041 _Reinhard Zumkeller_, Nov 28 2004