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 A071823 #8 Jun 29 2017 11:50:35
%S A071823 0,0,1,1,1,2,3,3,4,4,5,6,6,7,7,7,7,8,9,9,10,11,12,13,13,13,14,15,15,
%T A071823 15,16,16,17,17,18,19,19,20,20,20,20,21,22,23,23,24,25,26,27,27,27,27,
%U A071823 27,28,29,30,31,31,32,32,32,33,34,34,34,35,36,36,37,38,39,40,40,40,40,41
%N A071823 Number of numbers x <= n with largest prime factor of the form 4k+3.
%C A071823 Conjecture : for n > 1000, a(n) - n/2 > sqrt(n).
%t A071823 Accumulate[Table[If[Mod[FactorInteger[n][[-1,1]],4]==3,1,0],{n,80}]] (* _Harvey P. Dale_, Jun 29 2017 *)
%o A071823 (PARI) for(n=2,200,print1(sum(i=2,n,if((component(component(factor(i),1),omega(i))-3)%4,0,1)),","))
%K A071823 easy,nonn
%O A071823 1,6
%A A071823 _Benoit Cloitre_, Jun 07 2002
%E A071823 Zero prepended by _Harvey P. Dale_, Jun 29 2017