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 A168638 #9 Jul 28 2016 22:39:10
%S A168638 6,10,12,14,15,18,20,21,22,24,26,28,30,33,34,35,36,38,39,40,42,44,45,
%T A168638 46,48,50,51,52,54,55,56,57,58,60,62,63,65,66,68,69,70,72,74,75,76,77,
%U A168638 78,80,82,84,85,86,87,88,90,91,92,93,94,95,96,98,99,100,102,104,105,106
%N A168638 Number of distinct prime divisors of n is 2 or 3.
%H A168638 G. C. Greubel, <a href="/A168638/b168638.txt">Table of n, a(n) for n = 1..1000</a>
%F A168638 a(n) ~ A033992(n) ~ 2n log n / (log log n)^2. - _Charles R Greathouse IV_, Jul 28 2016
%e A168638 2310=2*3*5*7*11 has 5 prime factors, hence it is not here, but it is part of A064040.
%t A168638 Select[Range[106],MemberQ[{2,3},PrimeNu[#]]&] (* _Jayanta Basu_, Jun 04 2013 *)
%o A168638 (PARI) is(n)=my(o=omega(n)); o==2 || o==3 \\ _Charles R Greathouse IV_, Jul 28 2016
%K A168638 nonn
%O A168638 1,1
%A A168638 _Juri-Stepan Gerasimov_, Dec 01 2009